ASARCO INC
SC 14D1/A, 1999-10-08
PRIMARY SMELTING & REFINING OF NONFERROUS METALS
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<PAGE>
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549
                            ------------------------

                                 SCHEDULE 14D-1

                               (AMENDMENT NO. 1)

                             TENDER OFFER STATEMENT

      PURSUANT TO SECTION 14(D) (1) OF THE SECURITIES EXCHANGE ACT OF 1934

                                      AND
                               AMENDMENT NO. 5 TO
                                  SCHEDULE 13D
                   UNDER THE SECURITIES EXCHANGE ACT OF 1934
                            ------------------------

                              ASARCO INCORPORATED

                           (Name of Subject Company)

                               ASMEX CORPORATION
                                      AND
                           GRUPO MEXICO, S.A. DE C.V.
                                   (Bidders)
                            ------------------------

                           COMMON STOCK, NO PAR VALUE
                        (INCLUDING THE ASSOCIATED JUNIOR
                 PARTICIPATING PREFERRED STOCK PURCHASE RIGHTS)
                         (Title of Class of Securities)
                            ------------------------

                                    04341310
                     (CUSIP Number of Class of Securities)
                            ------------------------

                            Daniel Tellechea Salido
                Managing Director for Administration and Finance
                           Grupo Mexico, S.A. de C.V.
                              Baja California 200
                                Colonia Roma Sur
                           06760 Mexico City, Mexico

                          Telephone: 011-525-574-2067

          (Name, Address and Telephone Number of Person Authorized To
            Receive Notices and Communications on Behalf of Bidders)

                                    COPY TO:

                            Lori Anne Czepiel, Esq.
                                Brown & Wood LLP
                             One World Trade Center
                            New York, New York 10048
                           Telephone: (212) 839-5300
                           Facsimile: (212) 839-5599

                           CALCULATION OF FILING FEE

<TABLE>
<S>                                                                                     <C>
Transaction Valuation*                                                                  $1,062,632,096
Amount of Filing Fee**                                                                  $     212,527
</TABLE>

- ------------------------

*   Estimated for purposes of calculating the filing fee only. This filing fee
    calculation assumes the purchase of 36,021,427 shares of Common Stock,
    without par value, of ASARCO Incorporated at a price of $29.50 per share in
    cash without interest.

**  Calculated as 1/50 of 1% of the transaction value in accordance with Rule
    0-11(d) of the Securities Exchange Act of 1934, as amended.

/X/  Check box if any part of the fee is offset as provided by Rule 0-11(a)(2)
    and identify the filing with which the offsetting fee was previously paid.
    Identify the previous filing by registration statement number, of the Form
    or Schedule and the date of its filing.

<TABLE>
<S>                                  <C>
Amount Previously Paid:............  $186,594
Filing Party:......................  ASMEX Corporation and Grupo Mexico, S.A. de C.V.
Form or Registration No:...........  Schedule 14D-1 and Amendment No. 4 to Schedule 13D
Date Filed:........................  September 27, 1999
</TABLE>

- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
    This Amendment No. 1 to the Tender Offer Statement on Schedule 14D-1 and the
Schedule 13D as the same may have been amended from time to time (as amended
hereby, the 'Statement') relates to the offer by Grupo Mexico, S.A. de C.V., a
Mexican corporation ("Parent") through its wholly owned subsidiary, ASMEX
Corporation, a Delaware corporation ("Purchaser"), to purchase all of the
outstanding shares of common stock, without par value (together with the
associated junior participating preferred stock purchase rights, the "Common
Stock"), of ASARCO Incorporated, a New Jersey corporation (the "Company"), at a
purchase price of $29.50 per share of Common Stock, net to the seller in cash,
without interest thereon, upon the terms and subject to the conditions set forth
in the Offer to Purchase dated September 27, 1999 (the "Offer to Purchase"), a
copy of which is attached to this Statement as Exhibit (a)(1), and as amended
and supplemented by the Supplement thereto, dated October 8, 1999 (the
"Supplement") a copy of which is attached to this Statement as Exhibit (a)(10),
and in the related Letter of Transmittal, a copy of which is attached to this
Statement as Exhibit (a)(2) (which, as may be amended or supplemented from time
to time, together with the Offer to Purchase constitute the "Offer").

ITEM 1. SECURITY AND SUBJECT COMPANY.

    Item 1 is hereby amended and supplemented by the following:

    (b) The information set forth in the "INTRODUCTION" and "Section 1--Terms of
the Offer; Expiration Date" in the Supplement is incorporated herein by
reference.

    (c) The information set forth in "Section 3--Price Range of Shares;
Dividends" in the Supplement is incorporated herein by reference.

ITEM 3. PAST CONTACTS, TRANSACTIONS OR NEGOTIATIONS WITH THE SUBJECT COMPANY.

    Item 3 is hereby amended and supplemented by the following:

    (a)-(b) The information set forth in the "INTRODUCTION" and "Section
5--Background of the Offer; Contacts with the Company" in the Supplement is
incorporated herein by reference.

ITEM 4. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

    Item 4 is hereby amended and supplemented by the following:

    (a) The information set forth in "Section 4--Source and Amount of Funds" in
the Supplement is incorporated herein by reference.

ITEM 7. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT TO
  THE SUBJECT COMPANY'S SECURITIES

    Item 7 is hereby amended and supplemented by the following:

    The information set forth in the "INTRODUCTION" and "Section 5--Background
of the Offer; Contacts with the Company" in the Supplement is incorporated
herein by reference.

ITEM 10. ADDITIONAL INFORMATION.

    Item 10 is hereby amended and supplemented by the following:

    (b)-(c) The information set forth in "Section 7--Certain Legal Matters;
Regulatory Approvals; Certain Litigation" in the Supplement is incorporated
herein by reference.

                                       2
<PAGE>
ITEM 11. MATERIAL TO BE FILED AS EXHIBITS

<TABLE>
<S>        <C>
(a)(1)     Offer to Purchase dated September 27, 1999.*

(a)(2)     Form of Letter of Transmittal.*

(a)(3)     Form of Notice of Guaranteed Delivery.*

(a)(4)     Form of Letter to Brokers, Dealers, Commercial Banks, Trust Companies and
           Other Nominees.*

(a)(5)     Form of Letter to Clients for use by Brokers, Dealers, Commercial Banks, Trust
           Companies and Other Nominees.*

(a)(6)     Form of Guidelines for Certification of Taxpayer Identification Number on
           Substitute Form W-9.*

(a)(7)     Form of Summary Advertisement dated September 27, 1999.*

(a)(8)     Press release of Parent dated September 24, 1999.*

(a)(9)     Press release of Parent dated September 27, 1999.*

(a)(10)    Supplement to the Offer to Purchase dated October 7, 1999.

(a)(11)    Press release of Parent dated October 7, 1999.

(b)(1)     Commitment Letter from The Chase Manhattan Bank and Chase Securities Inc.
           dated September 24, 1999.*

(b)(2)     First Amended and Restated Commitment Letter from The Chase Manhattan Bank and
           Chase Securities Inc. dated October 5, 1999.

(b)(3)     Second Amended and Restated Commitment Letter from The Chase Manhattan Bank
           and Chase Securities Inc. dated October 7, 1999.

(c)        Not applicable.

(d)        Not applicable.

(e)        Not applicable.

(f)        None.

(g)(1)     1997 Annual Report of Parent.*

(g)(2)     1998 Annual Report of Parent.*

(g)(3)     Unaudited Financial Report of Parent as of June 30, 1999.*
</TABLE>

- ------------------------

*Previously filed.

                                       3
<PAGE>
                                   SIGNATURE

    After due inquiry and to the best of its knowledge and belief, the
undersigned certifies that the information set forth in this statement is true,
complete and correct.

Dated: October 8, 1999

<TABLE>
<S>                             <C>  <C>
                                GRUPO MEXICO, S.A. DE C.V.

                                By:  /s/ DANIEL TELLECHEA SALIDO
                                     ------------------------------------------
                                     Name: Daniel Tellechea Salido
                                     Title:  Managing Director for
                                     Administration
                                             and Finance

                                GRUPO MEXICO, S.A. DE C.V.

                                By:  /s/ GENARO GUERRERO DIAZ MERCADO
                                     ------------------------------------------
                                     Name: Genaro Guerrero Diaz Mercado
                                     Title:  Treasurer

                                ASMEX CORPORATION

                                By:  /s/ DANIEL TELLECHEA SALIDO
                                     ------------------------------------------
                                     Name: Daniel Tellechea Salido
                                     Title:  Vice President and Treasurer
</TABLE>

                                       4
<PAGE>
                                 EXHIBIT INDEX

<TABLE>
<CAPTION>
EXHIBIT NO.
- -----------------

<S>                <C>
(a)(1)             Offer to Purchase dated September 27, 1999.*

(a)(2)             Form of Letter of Transmittal.*

(a)(3)             Form of Notice of Guaranteed Delivery.*

(a)(4)             Form of Letter to Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees.*

(a)(5)             Form of Letter to Clients for use by Brokers, Dealers, Commercial Banks, Trust Companies and Other
                   Nominees.*

(a)(6)             Form of Guidelines for Certification of Taxpayer Identification Number on Substitute Form W-9.*

(a)(7)             Form of Summary Advertisement dated September 27, 1999.*

(a)(8)             Press release of Parent dated September 24, 1999.*

(a)(9)             Press release of Parent dated September 27, 1999.*

(a)(10)            Supplement to the Offer to Purchase dated October 7, 1999.

(a)(11)            Press release of Parent dated October 7, 1999.

(b)(1)             Commitment Letter from The Chase Manhattan Bank and Chase Securities Inc. dated September 24,
                   1999.*

(b)(2)             First Amended and Restated Commitment Letter from The Chase Manhattan Bank and Chase Securities
                   Inc. dated October 5, 1999.

(b)(3)             Second Amended and Restated Commitment Letter from The Chase Manhattan Bank and Chase Securities
                   Inc. dated October 7, 1999.

(c)                Not applicable.

(d)                Not applicable.

(e)                Not applicable.

(f)                None.

(g)(1)             1997 Annual Report of Parent.*

(g)(2)             1998 Annual Report of Parent.*

(g)(3)             Unaudited Financial Report of Parent as of June 30, 1999.*
</TABLE>

- ------------------------

*   Previously filed.

                                       5

<PAGE>
                                                               Exhibit 99(a)(10)

           SUPPLEMENT TO THE OFFER TO PURCHASE DATED OCTOBER 8, 1999

                               ASMEX CORPORATION

                          A WHOLLY OWNED SUBSIDIARY OF
                           GRUPO MEXICO, S.A. DE C.V.
                         HAS INCREASED THE PRICE OF ITS
                           OFFER TO PURCHASE FOR CASH
                 ALL OF THE OUTSTANDING SHARES OF COMMON STOCK
(INCLUDING THE ASSOCIATED JUNIOR PARTICIPATING PREFERRED STOCK PURCHASE RIGHTS)
                                       OF
                              ASARCO INCORPORATED
                                       TO
                              $29.50 NET PER SHARE

         THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT,
                NEW YORK CITY TIME, ON MONDAY, OCTOBER 25, 1999,
                         UNLESS THE OFFER IS EXTENDED.

    THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, (1) THERE BEING VALIDLY
TENDERED AND NOT PROPERLY WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER THAT
NUMBER OF SHARES OF COMMON STOCK (INCLUDING THE ASSOCIATED JUNIOR PARTICIPATING
PREFERRED STOCK PURCHASE RIGHTS (INCLUDING ANY SUCCESSORS THERETO, THE
"RIGHTS")), WITHOUT PAR VALUE (THE "COMMON STOCK"), OF ASARCO INCORPORATED
("ASARCO"), WHICH, TOGETHER WITH SHARES OF COMMON STOCK OWNED BY GRUPO MEXICO,
S.A. DE C.V. ("PARENT"), CONSTITUTE AT LEAST 80% OF THE SHARES OF COMMON STOCK
OUTSTANDING ON A FULLY DILUTED BASIS, (2) THE RIGHTS HAVING BEEN REDEEMED BY THE
BOARD OF DIRECTORS OF ASARCO OR ASMEX CORPORATION ("PURCHASER") BEING SATISFIED,
IN ITS SOLE DISCRETION, THAT THE RIGHTS ARE INVALID OR OTHERWISE INAPPLICABLE TO
THE TRANSACTIONS CONTEMPLATED BY THE OFFER TO PURCHASE OF PURCHASER, DATED
SEPTEMBER 27, 1999, AS SUPPLEMENTED HEREBY AND (3) THE PURCHASER BEING
SATISFIED, IN ITS SOLE DISCRETION, THAT THE AGREEMENT AND PLAN OF MERGER DATED
AS OF OCTOBER 5, 1999, AMONG ASARCO, PHELPS DODGE CORPORATION AND AAV
CORPORATION, HAS BEEN TERMINATED AND ASARCO HAVING ENTERED INTO A DEFINITIVE
MERGER AGREEMENT WITH PARENT AND PURCHASER TO PROVIDE FOR THE ACQUISITION OF
ASARCO BY PARENT OR PURCHASER.

                             ---------------------

          THE OFFER IS NOT CONDITIONED UPON PURCHASER OBTAINING FINANCING.

                             ---------------------

                                   IMPORTANT

    PARENT INTENDS TO SEEK TO RESUME NEGOTIATIONS WITH ASARCO WITH RESPECT TO
THE ACQUISITION OF ASARCO BY PARENT OR PURCHASER. PURCHASER RESERVES THE RIGHT
TO AMEND THE OFFER UPON ENTERING INTO A MERGER AGREEMENT WITH ASARCO.

    Any shareholder desiring to tender all or any portion of such shareholder's
shares of Common Stock should either (i) complete and sign the Letter of
Transmittal (or a facsimile thereof) in accordance with the instructions in the
Letter of Transmittal, have such shareholder's signature thereon guaranteed if
required by Instruction 1 to the Letter of Transmittal, mail or deliver the
Letter of Transmittal (or such facsimile thereof) and any other required
documents to the Depositary and either deliver the certificates for such shares
of Common Stock and, if separate, the certificates representing the associated
Rights to the Depositary along with the Letter of Transmittal (or a facsimile
thereof) or deliver such shares of Common Stock (and, if applicable, Rights)
pursuant to the procedure for book-entry transfer set forth in Section 3 of the
Offer to Purchase prior to the expiration of the Offer or (ii) request such
shareholder's broker, dealer, commercial bank, trust company or other nominee to
effect the transaction for such shareholder. A shareholder having shares of
Common Stock (and, if applicable, Rights) registered in the name of a broker,
dealer, commercial bank, trust company or other nominee must contact such
broker, dealer, commercial bank, trust company or other nominee if such
shareholder desires to tender such shares of Common Stock (and, if applicable,
Rights).

    Any shareholder who desires to tender shares of Common Stock (and, if
applicable, Rights) and whose certificates for such shares (and, if applicable,
Rights) are not immediately available, or who cannot comply with the procedures
for book-entry transfer described in the Offer to Purchase on a timely basis,
may tender such shares of Common Stock (and, if applicable, Rights) by following
the procedures for guaranteed delivery set forth in Section 3 of the Offer to
Purchase.

    Questions and requests for assistance may be directed to the Information
Agent (as defined herein) or the Dealer Manager (as defined herein) at their
respective addresses and telephone numbers set forth on the back cover of the
Offer to Purchase. Additional copies of the original Offer to Purchase, this
Supplement, the Letter of Transmittal or other tender offer materials may be
obtained from the Information Agent.

                             ---------------------

                      THE DEALER MANAGER FOR THE OFFER IS:

                             CHASE SECURITIES INC.

October 8, 1999
<PAGE>
                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                                    PAGE
                                                                                                                  ---------
<C>        <S>                                                                                                    <C>
INTRODUCTION....................................................................................................          1
       1.  Terms of the Offer; Expiration Date..................................................................          7
       2.  Procedures for Tendering Common Shares...............................................................          7
       3.  Price Range of Shares; Dividends.....................................................................          8
       4.  Source and Amount of Funds...........................................................................          8
       5.  Background of the Offer; Contacts with the Company...................................................          8
       6.  Conditions of the Offer..............................................................................         15
       7.  Certain Legal Matters; Regulatory Approvals; Certain Litigation......................................         17
       8.  Miscellaneous........................................................................................         17
</TABLE>

                                       i
<PAGE>
TO THE HOLDERS OF COMMON STOCK OF ASARCO INCORPORATED:

                                  INTRODUCTION

    The following information amends and supplements the Offer to Purchase,
dated September 27, 1999 (the "Offer to Purchase"; capitalized terms not defined
herein having the meanings ascribed therein), of ASMEX Corporation
("Purchaser"), a Delaware corporation and a wholly owned subsidiary of Grupo
Mexico, S.A. de C.V., a Mexican corporation ("Parent"), pursuant to which
Purchaser is offering to purchase all of the outstanding shares of common stock,
without par value (the "Common Stock"), of ASARCO Incorporated, a New Jersey
corporation ("ASARCO"), including the associated Junior Participating Preferred
Stock Purchase Rights (the "Rights") issued pursuant to the Rights Agreement,
dated as of January 28, 1998, as amended as of July 15, 1999, between ASARCO and
The Bank of New York, as Rights Agent (as such agreement may be further amended
and including any successor agreement, the "Rights Agreement"), at a price of
$29.50 per share of Common Stock, net to the seller in cash, without interest
thereon (the "Offer Price"), upon the terms and subject to the conditions set
forth in the Offer to Purchase, this Supplement and in the Letter of Transmittal
(which, as amended from time to time, together constitute the "Offer"). Unless
the context otherwise requires, all references to Common Stock shall include the
associated Rights, and all references to the Rights shall include the benefits
that may inure to holders of the Rights pursuant to the Rights Agreement,
including the right to receive any payment due upon redemption of the Rights.

    The purpose of the Offer and the Proposed Merger is to enable Parent to
acquire control of, and ultimately the entire equity interest in, ASARCO. The
Offer, as the first step in the acquisition of ASARCO, is intended to facilitate
the acquisition of that number of shares of Common Stock that, together with
shares of Common Stock owned by Parent and Purchaser, would constitute at least
80% of the shares of Common Stock on a fully diluted basis. Article 7 of
ASARCO'S Restated Certificate of Incorporation (the "ASARCO Certificate of
Incorporation") appears to require the affirmative vote of at least 80% of the
outstanding shares of Common Stock to approve a transaction such as the Proposed
Merger. Parent intends to seek to resume negotiations with ASARCO with respect
to the acquisition of ASARCO by Parent or Purchaser in order to enter into a
definitive merger agreement providing for such acquisition. Parent currently
intends, as soon as practicable following consummation of the Offer pursuant to
such a merger agreement or, if practicable, prior to the scheduled Expiration
Date of the Offer, to seek to have Purchaser consummate a merger with and into
ASARCO, with ASARCO continuing as the surviving corporation (the "Proposed
Merger"), pursuant to which each then outstanding share of Common Stock (other
than shares of Common Stock owned by Parent or any of its wholly owned
subsidiaries and shares of Common Stock held in the treasury of ASARCO) would be
converted into the right to receive in cash the price per share paid by
Purchaser pursuant to the Offer. In general, in the event that the Proposed
Merger is consummated as described above, gain or loss will be recognized by a
shareholder of ASARCO who receives cash in exchange for shares of Common Stock
pursuant to the Offer and/or the Proposed Merger. See Section 5 of the Offer to
Purchase.

    This Supplement should be read in conjunction with the Offer to Purchase.
Except as set forth in this Supplement, the terms and conditions previously set
forth in the Offer to Purchase, and the Letter of Transmittal mailed with the
Offer to Purchase, remain applicable in all respects to the Offer. Terms used
but not defined herein have the meanings set forth in the Offer to Purchase.

    On Monday, September 27, 1999, ASARCO filed an amendment to the ASARCO
Schedule 14D-9 with respect to the Phelps Dodge Exchange Offer announcing
certain changes that the ASARCO Board had adopted to its compensation and stock
option plans.

    On Wednesday, September 29, 1999, Parent's legal and financial advisors met
with ASARCO's legal and financial advisors to discuss ASARCO's intended
procedures going forward in light of the Offer, the competing Phelps Dodge
Exchange Offer for the Common Stock and the Proposed Cyprus Amax Transaction.

                                       1
<PAGE>
    On Thursday, September 30, 1999, Cyprus Amax notified ASARCO that it was
terminating the Cyprus Amax Agreement and paid ASARCO a $45 million termination
fee. Phelps Dodge and Cyprus Amax then issued a press release publicly
announcing that they had signed a definitive merger agreement under which Phelps
Dodge will acquire Cyprus Amax for $7.61 in cash and 0.2203 shares of Phelps
Dodge Common Stock per Cyprus Amax share on a fully prorated basis.

    Also on September 30, the ASARCO Board determined to postpone the occurrence
of a Distribution Date for purposes of the Rights Agreement as a result of the
public announcement of the Offer until such later date as determined by the
ASARCO Board. On the evening of September 30, Parent was provided by ASARCO's
legal advisors with a form of merger agreement acceptable to ASARCO.

    On Friday evening, October 1, 1999, Mr. McAllister and Mr. Larrea met in
Mexico City and discussed the Offer. During that conversation, Mr. Larrea
proposed that ASARCO enter into a merger agreement with Parent and Purchaser at
$26.00 per share. Mr. McAllister said that he did not believe the ASARCO Board
would be prepared to take such action at that time.

    On Saturday, October 2, 1999, Parent's legal advisors delivered to ASARCO
Parent's proposed revisions to the form of merger agreement that ASARCO had
previously delivered. On Sunday, October 3, 1999, the legal advisors to Parent
and ASARCO met to discuss the terms of a proposed merger agreement. A revised
form of merger agreement was delivered by ASARCO to Parent's legal advisors late
on Sunday, October 3, 1999.

    On Monday, October 4, 1999, ASARCO's financial advisors telephonically
informed Parent's financial advisor that ASARCO would be conducting an "auction"
for the sale of ASARCO. Later that day, Mr. Larrea sent a letter to Mr.
McAllister to express his dissatisfaction with the process established to
determine ASARCO's proposed ultimate acquiror. Still later on October 5, 1999,
ASARCO delivered written procedures governing the "auction."

    On Tuesday, October 5, 1999, ASARCO filed a Solicitation/Recommendation
Statement on Schedule 14D-9 with respect to the Offer, recommending that
shareholders of ASARCO reject the Offer and not tender their shares pursuant
thereto. That evening, representatives of Parent's legal and financial advisors
submitted a bid package to ASARCO pursuant to its established procedures, the
material terms of which were set forth in the following cover letter:

                                                                 October 5, 1999

       BY HAND

       Board of Directors of ASARCO Incorporated
       c/o J. Michael Schell, Esq.
       Skadden, Arps, Slate, Meagher & Flom LLP
       919 Third Avenue
       New York, NY 10022

       Ladies and Gentlemen:

           In accordance with the procedures communicated to us by the ASARCO
       Board, we are pleased to submit the proposal of Grupo Mexico, S.A. de
       C.V., through its wholly-owned subsidiary, ASMEX Corporation, which will
       be irrevocable until 10:00 a.m. Thursday, October 7, 1999, to acquire all
       of the outstanding common stock of ASARCO at a price of $26.00 per share
       (the "Proposal"). We are prepared to enter into the form of merger
       agreement previously submitted to us by ASARCO's attorneys on October 3,
       1999 with those revisions that are reflected in the enclosed mark-up of
       that agreement (as so revised, the "Proposed Agreement"). The price
       stated in our Proposal reflects our previously expressed disagreement
       with the "auction" procedures that you have employed.

                                       2
<PAGE>
           Our Proposal is fully financed as evidenced by the enclosed
       commitment letter from The Chase Manhattan Bank and Chase Securities
       Inc., which has been amended and restated today in order to narrow
       certain conditions originally reflected therein. Under the terms of the
       amended commitment letter, the narrowed conditions will not, however,
       become effective if we have not signed a merger agreement by 5:00 p.m. on
       October 8, 1999. Our Proposal contemplates the dual-track structure
       discussed by our respective counsel of proceeding with a tender offer and
       a call for a shareholders meeting. As a result of the negotiations with
       our lender to obtain these more limited conditions, the tender offer
       would close twenty business days from the date of its amendment. The
       total amount of the funds required to effect the transaction will be
       provided by our working capital resources plus the amounts to be supplied
       under the commitment letter. Our Proposal is fully authorized and no
       further corporate action by Grupo Mexico is required.

           The Proposed Agreement is subject to the following material
       conditions:

        (i) the conditions set forth in Article VI of the Proposed Agreement;
            and

        (ii) a condition with respect to disruption of the financial markets
             that reflects the language of the corresponding condition in our
             commitment letter, which is significantly narrower for the period
             prior to November 30, 1999 than was the case under our commitment
             letter prior to its amendment.

           The Proposed Agreement also provides for a termination fee in the
       amount of $30 million in the following circumstances:

        (i) If ASARCO breaches the "No Shop" provision of Section 5.7 of the
            Proposed Agreement;

        (ii) If ASARCO enters into an alternative transaction with a third party
             in accordance with the "fiduciary out" and "match" right provisions
             of Section 5.7 of the Proposed Agreement;

       (iii) If ASARCO withdraws or adversely modifies its recommendation to its
             shareholders of the transactions contemplated by the Proposed
             Agreement; and

        (iv) If the ASARCO shareholders do not approve the transactions
             contemplated by the Proposed Agreement at ASARCO's shareholder
             meeting and at such time there is a pending competing acquisition
             proposal that has been announced.

           In addition, we have been advised by the relevant regulatory
       authorities that the only barrier to our receipt of notice of early
       termination under the Hart-Scott-Rodino Antitrust Improvements Act of
       1976 is the required filing by ASARCO of its report form. Should we
       receive early termination prior to execution of the Proposed Agreement,
       we would be willing to conform Section 5.4 to the version of Section 5.4
       contained in the September 30, 1999 draft of the merger agreement
       submitted to us by your attorneys.

           In the event you choose to proceed with our Proposal, we will require
       a period of exclusivity for the limited period of time that would be
       necessary to clarify any outstanding matters and arrive at a
       comprehensive agreement.

                                       3
<PAGE>
           We look forward to receiving a prompt and favorable response to this
       Proposal so that we can proceed to finalize this transaction.
       Notwithstanding your adopted procedures, which we received today, we hope
       that you will leave the auction process open if you do not choose to
       accept this Proposal.

                                          Very truly yours,

<TABLE>
<S>                             <C>
                                Grupo Mexico, S.A. de C.V.

                                /s/ DANIEL TELLECHEA SALIDO
                                -----------------------------------
                                Daniel Tellechea Salido
                                Managing Director for Administration
                                and Finance and Alternate Director

                                /s/ GENARO GUERRERO DIAZ MERCADO
                                -----------------------------------
                                Genaro Guerrero Diaz Mercado
                                Treasurer
</TABLE>

    On Wednesday, October 6, 1999, ASARCO and Phelps Dodge issued a press
release publicly announcing that they had entered into a merger agreement
providing for an increase in the terms of the revised Phelps Dodge Exchange
Offer for ASARCO Common Stock (the "PD Merger Agreement"). According to a Form
8-K filed by ASARCO on the same day, the PD Merger Agreement provides an
all-cash election for ASARCO shareholders of $29.50 per share of Common Stock
and an all-stock election of 0.50266 shares of Phelps Dodge Common Stock per
share of Common Stock, subject to proration. However, assuming full proration,
the PD Merger Agreement provides for an exchange of $14.75 in cash and 0.2513
shares of Phelps Dodge Common Stock for each share of Common Stock on a fully
prorated basis.

    In the PD Merger Agreement, ASARCO has agreed to a provision (the "No
Solicitation Provision") that none of ASARCO, its subsidiaries or any of their
respective directors, officers, employees, investment bankers, financial
advisors, attorneys, accountants or other representatives will, directly or
indirectly through another person, (i) solicit, initiate or encourage (including
by way of furnishing information), or take any other action designed to
facilitate, any inquiries or the making of any proposal which constitutes an
ASARCO Takeover Proposal (as defined herein) or reasonably could be expected to
lead to an ASARCO Takeover Proposal, or (ii) participate in any discussions or
negotiations regarding any ASARCO Takeover Proposal; provided, however, that if
the ASARCO Board determines in good faith, after consultation with outside
counsel, that it is necessary to do so in order to comply with its fiduciary
duties to ASARCO's shareholders under applicable law, ASARCO may, in response to
an ASARCO Takeover Proposal which was not solicited by it or which did not
otherwise result from a breach of the No Solicitation Provision, and subject to
providing prior written notice of its decision to take such action to Phelps
Dodge (the "ASARCO Notice"), (x) furnish information with respect to ASARCO and
its subsidiaries to any person making an ASARCO Takeover Proposal pursuant to a
customary confidentiality agreement (as determined by ASARCO after consultation
with its outside counsel) and (y) participate in discussions or negotiations
regarding such ASARCO Takeover Proposal. The No Solicitation Provision further
provides that neither the ASARCO Board nor any committee thereof shall (i)
withdraw or modify, or propose publicly to withdraw or modify, in a manner
adverse to Phelps Dodge, the recommendation by such board of directors or such
committee of the proposed merger with Phelps Dodge (the "Proposed PD Merger") or
the PD Merger Agreement, (ii) approve or recommend, or propose publicly to
approve or recommend, any ASARCO Takeover Proposal, or (iii) cause ASARCO to
enter into any letter of intent, agreement in principle, acquisition agreement
or other similar agreement (each, an "ASARCO Acquisition Agreement") related to
any ASARCO Takeover Proposal. Notwithstanding the foregoing, in the event that

                                       4
<PAGE>
the ASARCO Board receives an ASARCO Takeover Proposal and the ASARCO Board
determines in good faith, after consultation with outside counsel, that it is
necessary to do so in order to comply with its fiduciary duties to ASARCO's
shareholders under applicable law, the ASARCO Board may (x) take any of the
actions described in clauses (i), (ii) or (iii) of the preceding sentence or (y)
terminate the PD Merger Agreement (and concurrently with or after such
termination, if it so chooses, cause ASARCO to enter into any ASARCO Acquisition
Agreement with respect to any ASARCO Takeover Proposal) but only after the fifth
business day following Phelps Dodge's receipt of written notice advising Phelps
Dodge that the ASARCO Board is prepared to accept an ASARCO Takeover Proposal,
specifying the material terms and conditions of such ASARCO Takeover Proposal
and identifying the person making such ASARCO Takeover Proposal.

    As used in the PD Merger Agreement, the term "ASARCO Takeover Proposal"
means any inquiry, proposal or offer (or any improvement, restatement,
amendment, renewal or reiteration thereof) from any person relating to any
direct or indirect acquisition or purchase of a business or shares of any class
of equity securities of ASARCO or any of its subsidiaries, any tender offer or
exchange offer that, if consummated, would result in any person beneficially
owning any class of equity securities of ASARCO or any of its subsidiaries, or
any merger, consolidation, business combination, recapitalization, liquidation,
dissolution or similar transaction involving ASARCO or any of its subsidiaries,
other than the Proposed PD Merger (provided that an ASARCO Takeover Proposal
will have to exceed certain financial or ownership thresholds in order to
require payment of the ASARCO Termination Fee).

    The PD Merger Agreement also provides that ASARCO shall be liable to Phelps
Dodge for a termination fee of $30 million payable by wire transfer of same day
funds (the "ASARCO Termination Fee") if (i) prior to the meeting of ASARCO
shareholders to consider and vote upon the Proposed PD Merger an ASARCO Takeover
Proposal shall have been made known to ASARCO or shall have been made directly
to its shareholders generally or any person shall have publicly announced an
intention (whether or not conditional) to make an ASARCO Takeover Proposal and
thereafter the PD Merger Agreement is terminated by either Phelps Dodge or
ASARCO in the event shares are not purchased pursuant to the Phelps Dodge
Exchange Offer for the Common Stock on or before March 31, 2000 or (ii) the PD
Merger Agreement is terminated by ASARCO in order to enter into an agreement to
accept an ASARCO Takeover Proposal; provided, however, that no ASARCO
Termination Fee shall be payable to Phelps Dodge unless and until within 18
months of such termination ASARCO or any of its subsidiaries enters into any
ASARCO Acquisition Agreement or consummates any ASARCO Takeover Proposal.

    Also on October 6, 1999, Parent and Purchaser received notice that they had
been granted early termination of the waiting period under the HSR Act. Later in
the evening of October 6, 1999, Mr. Larrea corresponded to Mr. McAllister to
register again his displeasure with the process employed by ASARCO in its
"auction."

    On October 7, 1999, Parent submitted to the ASARCO Board a letter detailing
the revised proposal to acquire ASARCO by Parent and Purchaser at the increased
Offer Price of $29.50 per share in cash. Subsequently, Parent issued the
following press release disclosing the delivery and contents of the letter:

                          GRUPO MEXICO INCREASES TENDER OFFER
                                TO ACQUIRE ASARCO INC.
                              TO $29.50 PER SHARE IN CASH

              Receives Early Termination to Hart-Scott-Rodino Waiting Period

           Mexico City (October 7, 1999)--Grupo Mexico, S.A. de C.V., announced
       today that it has revised its proposal to acquire all of the outstanding
       shares of ASARCO Incorporated (NYSE:AR) to increase the price to $29.50
       per share in cash. The revised offer, which values ASARCO at $2.24
       billion (including assumption of debt), is scheduled to expire at 12:00
       midnight, New York City time, on Monday, October 25, 1999, unless
       extended.

                                       5
<PAGE>
          Following the completion of the tender offer, Grupo Mexico intends to
      consumate a second step merger in which all remaining ASARCO shareholders
      will also receive the same cash price paid in the tender offer.

          Earlier today, Grupo Mexico sent the following letter to the Board of
      Directors of ASARCO:

                                                                 October 7, 1999

      Board of Directors
      ASARCO Incorporated
      180 Maiden Lane
      New York, NY 10038

      Attention: Francis R. McAllister
      Chairman and Chief Executive Officer

      Dear Members of the Board:

          Based on our assessment of the pending offer by Phelps Dodge
      Corporation as reflected in your announced agreement with them, and our
      view of the intrinsic value in ASARCO Incorporated that Grupo Mexico, S.A.
      de C.V., could realize if Grupo Mexico owned ASARCO, we are today
      increasing the price in our September 27 tender offer to ASARCO
      shareholders for all outstanding shares of ASARCO to $29.50 per share in
      cash. The other terms of our September 27 tender offer remain
      substantially unchanged.

          Our revised offer provides value to your shareholders that is
      demonstrably superior to your agreement with Phelps Dodge. This offer
      represents a premium of 59% over the value of your recently announced
      agreement with Phelps Dodge based upon the October 6, 1999 closing price
      of $53.00 per share for Phelps Dodge common stock, and a premium of 59%
      over ASARCO's unaffected stock price on August 20, 1999, immediately prior
      to the announcement of Phelps Dodge's proposal.

          As a result, we believe that you can, and indeed are obligated to,
      meet with us and discuss our revised offer. Accordingly, we request that,
      pursuant to Section 5.9 of your agreement with Phelps Dodge, you elicit
      such advice and make such determinations in view of your fiduciary duties
      such that ASARCO would be in a position to immediately engage in
      negotiations and discussions with us concerning our superior proposal. We
      also believe that you cannot, consistent with your fiduciary duties,
      continue to recommend to your shareholders the transaction with Phelps
      Dodge in light of our revised offer.

          As before, our execution of a merger agreement would not be contingent
      upon a due dilgence review. Furthermore, in view of the fact that we have
      been granted "early termination" of the waiting period under the
      Hart-Scott-Rodino Antitrust Improvements Act, we are confident that
      consummation of our proposed transaction is not subject to any material
      regulatory approvals.

          Our revised offer presents a compelling opportunity for ASARCO and its
      shareholders to improve upon your existing transaction with Phelps Dodge.

          Our offer, of course, continues to be conditioned upon entering into a
      negotiated agreement with you. As in the past, we are prepared to meet
      with you at any time to negotiate the terms of a merger agreement having
      substantially the same terms and conditions that were contained in the
      form of merger agreement that was submitted to you on October 5, 1999,
      modified to (i) remove our request for the "match" right in connection
      with competing proposals set forth in the "no-shop" provision and
      replacing it with the relevant provision in your Phelps Dodge Agreement,
      (ii) reflect the termination of your agreement with Phelps Dodge and (iii)
      incorporate certain provisions from your agreement with Phelps Dodge,
      provided that you enter into an agreement with us on or before October 15,
      1999.

                                       6
<PAGE>
          Please contact us to schedule a meeting of our respective advisors to
      bring this situation to a prompt and satisfactory conclusion for the
      shareholders of both of our companies.

<TABLE>
<S>                             <C>        <C>
                                Very truly yours,
                                GRUPO MEXICO, S.A. de C.V.

                                By         /s/ DANIEL TELLECHEA SALIDO
                                           ---------------------------
                                           Daniel Tellechea Salido
                                           Managing Director for Administrative
                                           and Finance and Alternative Director

                                By         /s/ GENARO GUERRERO DIAZ MERCADO
                                           -----------------------------------
                                           Genaro Guerrero Diaz Mercado
                                           Treasurer
</TABLE>

      cc:J. Michael Schell, Esq.
        Steven Koch

      Grupo Mexico is a diversified mining company that ranks among the world's
      largest copper, zinc and silver producers. The company's business includes
      mining, smelting and refining in Mexico and is one of the world's
      lowest-cost operations. Grupo Mexico also operates the largest railroad
      system in Mexico.

      NOTE: Statements in this press release include "forward-looking
      statements" that express expectations of future events or results. All
      statements based on future expectations rather than on historical facts
      are forward-looking statements that involve a number of risks and
      uncertainties, and the company cannot give assurance that such statements
      will prove to be correct.

    Parent intends to seek to resume negotiations with ASARCO with respect to
the acquisition of ASARCO by Parent or Purchaser, whether pursuant to the Offer
and the Proposed Merger, or otherwise. If such negotiations result in a
definitive merger agreement between ASARCO, Parent and Purchaser, the
consideration to be received by holders of shares of Common Stock would consist
of the right to receive an amount in cash equal to the Offer Price.

    This Supplement does not constitute a solicitation of proxies for any
meeting of ASARCO's shareholders. Any such solicitation by Parent or Purchaser
would be made only pursuant to separate proxy materials complying with the
requirements of the Exchange Act.

    THE OFFER TO PURCHASE, THIS SUPPLEMENT AND THE LETTER OF TRANSMITTAL CONTAIN
IMPORTANT INFORMATION WHICH SHOULD BE READ CAREFULLY BEFORE ANY DECISION IS MADE
WITH RESPECT TO THE OFFER.

    1. TERMS OF THE OFFER; EXPIRATION DATE.  The discussion set forth in Section
1 of the Offer to Purchase is hereby amended and supplemented as follows:

    The price to be paid for Common Stock purchased pursuant to the Offer has
been increased from $26.00 to $29.50 per share of Common Stock, net to the
seller in cash, without interest thereon, upon the terms and subject to the
conditions of the Offer. All shareholders whose shares of Common Stock are
tendered and purchased pursuant to the Offer (including those shares of Common
Stock tendered prior to the date hereof) will receive the increased purchase
price.

    2. PROCEDURES FOR TENDERING COMMON SHARES.  The discussion set forth in
Section 3 of the Offer to Purchase is hereby amended and supplemented as
follows:

    Tendering shareholders may continue to use the Letter of Transmittal and
Notice of Guaranteed Delivery previously distributed with the Offer to Purchase
to tender Common Stock. Shareholders should follow the procedures for tendering
Common Stock set forth in Section 3 of the Offer to Purchase.

                                       7
<PAGE>
    SHAREHOLDERS WHO HAVE PREVIOUSLY VALIDLY TENDERED SHARES OF COMMON STOCK
PURSUANT TO THE OFFER AND NOT PROPERLY WITHDRAWN SUCH SHARES OF COMMON STOCK
HAVE VALIDLY TENDERED SUCH SHARES OF COMMON STOCK FOR PURPOSES OF THE OFFER, AS
AMENDED, AND NEED NOT TAKE ANY FURTHER ACTION IN ORDER TO RECEIVE THE INCREASED
PRICE OF $29.50 PER SHARE OF COMMON STOCK PURSUANT TO THE OFFER.

    3. PRICE RANGE OF SHARES; DIVIDENDS.  The discussion set forth in Section 6
of the Offer to Purchase is hereby amended and supplemented as follows:

    According to public sources, the high and low sale prices of Common Stock as
reported by the NYSE Composite Tape for the third quarter of 1999 were $27 9/16
and $17 1/16, respectively; the high and low sale prices per share of Common
Stock for the fourth quarter of 1999 (through October 6, 1999) were $28 1/8 and
$26 9/16, respectively. On October 6, 1999, the last full trading day prior to
Parent's announcement that it was amending the terms of the Offer upon the terms
set forth in this Supplement, the reported closing sale price per share of
Common Stock as reported by the NYSE Composite Tape was $28. Shareholders are
urged to obtain a current market quotation for the Common Stock.

    4. SOURCE AND AMOUNT OF FUNDS.  The discussion set forth in Section 10 of
the Offer to Purchase is hereby amended and supplemented as follows:

    Purchaser estimates that the total amount of funds now required to purchase
Common Stock pursuant to the Offer (as described in this Supplement) and to pay
all related costs and expenses will be approximately $1,150 million.

    On October 5, 1999, the commitment letter, dated as of September 24, 1999
(the "Commitment Letter"), by and among Parent, The Chase Manhattan Bank and
Chase Securities Inc. (collectively, "Chase") was amended (the "First Amended
and Restated Commitment Letter") to modify certain conditions to the obligations
of Chase under the Credit Facilities in a manner favorable to Parent and to
provide a revised condition with respect to market disruptions that is more
narrow than the prior such condition until November 30, 1999, and that reverts
to its prior form thereafter. Such amendments to the commitment letter were
subject to a satisfactory merger agreement being entered into with ASARCO not
later than October 8, 1999.

    On October 7, 1999, the Commitment Letter was further amended (the "Second
Amended and Restated Committment Letter") to extend to October 15, 1999 the date
by which a merger agreement with ASARCO must be entered into, and to require
that any additional funds necessary to consummate the Offer as a result of the
increase in the price to be paid for Common Stock purchased in the Offer be
contributed as equity to the Purchaser from sources acceptable to Chase
Securities Inc.

    The foregoing supplemental description of the Credit Facilities is qualified
in its entirety by reference to the full text of the Commitment Letter, the
First Amended and Restated Commitment Letter and the Second Amended and Restated
Commitment Letter, copies of which have been filed with the SEC as exhibits to
the Parent Schedule 14D-1 and are incorporated by reference herein.

    5. BACKGROUND OF THE OFFER; CONTACTS WITH THE COMPANY.  The discussion set
forth in Section 11 of the Offer to Purchase is hereby amended and supplemented
as follows:

    On Monday, September 27, 1999, ASARCO filed an amended ASARCO Schedule 14D-9
with respect to the Phelps Dodge Exchange Offer announcing certain changes that
the ASARCO Board had adopted to its compensation and stock option plans.

    On Wednesday, September 29, 1999, Parent's legal and financial advisors met
with ASARCO's legal and financial advisors to discuss ASARCO's intended
procedures going forward in light of the Offer, the competing Phelps Dodge
Exchange Offer for the Common Stock and the Proposed Cyprus Amax Transaction.

    On Thursday, September 30, 1999, Cyprus Amax notified ASARCO that it was
terminating the Cyprus Amax Agreement and paid ASARCO a $45 million termination
fee. Phelps Dodge and Cyprus Amax then issued a press release publicly
announcing that they had signed a definitive merger agreement under which

                                       8
<PAGE>
Phelps Dodge will acquire Cyprus Amax for $7.61 in cash and 0.2203 shares of
Phelps Dodge Common Stock per Cyprus Amax share on a fully prorated basis.

    Also on September 30, the ASARCO Board determined to postpone the occurrence
of a Distribution Date for purposes of the Rights Agreement as a result of the
public announcement of the Offer until such later date as determined by the
ASARCO Board. On the evening of September 30, Parent was provided by ASARCO's
legal advisors with a form of merger agreement acceptable to ASARCO.

    On Friday evening, October 1, 1999, Mr. McAllister and Mr. Larrea met in
Mexico City and discussed the Offer. During that conversation, Mr. Larrea
proposed that ASARCO enter into a merger agreement with Parent and Purchaser at
$26.00 per share. Mr. McAllister said that he did not believe the ASARCO Board
would be prepared to take such action at that time.

    On Saturday, October 2, 1999, Parent's legal advisors delivered to ASARCO
Parent's proposed revisions to the form of merger agreement that ASARCO had
previously delivered. On Sunday, October 3, 1999, the legal advisors to Parent
and ASARCO met to discuss the terms of a proposed merger agreement. A revised
form of merger agreement was delivered by ASARCO to Parent's legal advisors late
on Sunday, October 3, 1999.

    Also, on Monday, October 4, 1999, ASARCO's financial advisors telephonically
informed Parent's financial advisor that ASARCO would be conducting an "auction"
for the sale of ASARCO. Later that day, Mr. Larrea sent a letter to Mr.
McAllister to express his dissatisfaction with the process established to
determine ASARCO's proposed ultimate acquiror. Still later on October 5, 1999,
ASARCO delivered written procedures governing the "auction."

    On Tuesday, October 5, 1999, ASARCO filed a Solicitation/Recommendation
Statement on Schedule 14D-9 with respect to the Offer, recommending that
shareholders of ASARCO reject the Offer and not tender their shares pursuant
thereto. That evening, representatives of Parent's legal and financial advisors
submitted a bid package to ASARCO pursuant to its established procedures, the
material terms of which were set forth in the following cover letter:

                                                                 October 5, 1999

        BY HAND

       Board of Directors of ASARCO Incorporated
       c/o J. Michael Schell, Esq.
       Skadden, Arps, Slate, Meagher & Flom LLP
       919 Third Avenue
       New York, NY 10022
       Ladies and Gentlemen:

           In accordance with the procedures communicated to us by the ASARCO
       Board, we are pleased to submit the proposal of Grupo Mexico, S.A. de
       C.V., through its wholly-owned subsidiary, ASMEX Corporation, which will
       be irrevocable until 10:00 a.m. Thursday, October 7, 1999, to acquire all
       of the outstanding common stock of ASARCO at a price of $26.00 per share
       (the "Proposal"). We are prepared to enter into the form of merger
       agreement previously submitted to us by ASARCO's attorneys on October 3,
       1999 with those revisions that are reflected in the enclosed mark-up of
       that agreement (as so revised, the "Proposed Agreement"). The price
       stated in our Proposal reflects our previously expressed disagreement
       with the "auction" procedures that you have employed.

                                       9
<PAGE>
           Our Proposal is fully financed as evidenced by the enclosed
       commitment letter from The Chase Manhattan Bank and Chase Securities
       Inc., which has been amended and restated today in order to narrow
       certain conditions originally reflected therein. Under the terms of the
       amended commitment letter, the narrowed conditions will not, however,
       become effective if we have not signed a merger agreement by 5:00 p.m. on
       October 8, 1999. Our Proposal contemplates the dual-track structure
       discussed by our respective counsel of proceeding with a tender offer and
       a call for a shareholders meeting. As a result of the negotiations with
       our lender to obtain these more limited conditions, the tender offer
       would close twenty business days from the date of its amendment. The
       total amount of the funds required to effect the transaction will be
       provided by our working capital resources plus the amounts to be supplied
       under the commitment letter. Our Proposal is fully authorized and no
       further corporate action by Grupo Mexico is required.

           The Proposed Agreement is subject to the following material
       conditions:

            (i) the conditions set forth in Article VI of the Proposed
                Agreement; and

            (ii) a condition with respect to disruption of the financial markets
                 that reflects the language of the corresponding condition in
                 our commitment letter, which is significantly narrower for the
                 period prior to November 30, 1999 than was the case under our
                 commitment letter prior to its amendment.

           The Proposed Agreement also provides for a termination fee in the
       amount of $30 million in the following circumstances:

            (i) If ASARCO breaches the "No Shop" provision of Section 5.7 of the
                Proposed Agreement;

            (ii) If ASARCO enters into an alternative transaction with a third
                 party in accordance with the "fiduciary out" and "match" right
                 provisions of Section 5.7 of the Proposed Agreement;

           (iii) If ASARCO withdraws or adversely modifies its recommendation to
                 its shareholders of the transactions contemplated by the
                 Proposed Agreement; and

            (iv) If the ASARCO shareholders do not approve the transactions
                 contemplated by the Proposed Agreement at ASARCO's shareholder
                 meeting and at such time there is a pending competing
                 acquisition proposal that has been announced.

           In addition, we have been advised by the relevant regulatory
       authorities that the only barrier to our receipt of notice of early
       termination under the Hart-Scott-Rodino Antitrust Improvements Act of
       1976 is the required filing by ASARCO of its report form. Should we
       receive early termination prior to execution of the Proposed Agreement,
       we would be willing to conform Section 5.4 to the version of Section 5.4
       contained in the September 30, 1999 draft of the merger agreement
       submitted to us by your attorneys.

           In the event you choose to proceed with our Proposal, we will require
       a period of exclusivity for the limited period of time that would be
       necessary to clarify any outstanding matters and arrive at a
       comprehensive agreement.

                                       10
<PAGE>
           We look forward to receiving a prompt and favorable response to this
       Proposal so that we can proceed to finalize this transaction.
       Notwithstanding your adopted procedures, which we received today, we hope
       that you will leave the auction process open if you do not choose to
       accept this Proposal.

                                      Very truly yours,

                                      Grupo Mexico, S.A. de C.V.

                                      By:  /S/ DANIEL TELLECHEA SALIDO
       -------------------------------------------------------------------------
                                          Daniel Tellechea Salido
                                          Managing Director for Administration
                                          and Finance and Alternate Director

                                      By:  /S/ GENARO GUERRERO DIAZ MERCADO
       -------------------------------------------------------------------------
                                          Genaro Guerrero Diaz Mercado
                                          Treasurer

    On Wednesday, October 6, 1999, ASARCO and Phelps Dodge issued a press
release publicly announcing that they had entered into the PD Merger Agreement
providing for an increase in the terms of the revised Phelps Dodge Exchange
Offer for ASARCO Common Stock. According to a Form 8-K filed by ASARCO on the
same day, the PD Merger Agreement provides an all-cash election for ASARCO
shareholders of $29.50 per share of Common Stock and an all-stock election of
0.50266 shares of Phelps Dodge Common Stock per share of Common Stock, subject
to proration. However, assuming full proration, the PD Merger Agreement provides
for an exchange of $14.75 in cash and 0.2513 shares of Phelps Dodge Common Stock
for each share of Common Stock on a fully prorated basis.

    In the PD Merger Agreement, ASARCO has agreed to the No Solicitation
Provision pursuant to which none of ASARCO, its subsidiaries or any of their
respective directors, officers, employees, investment bankers, financial
advisors, attorneys, accountants or other representatives will, directly or
indirectly through another person, (i) solicit, initiate or encourage (including
by way of furnishing information), or take any other action designed to
facilitate, any inquiries or the making of any proposal which constitutes an
ASARCO Takeover Proposal or reasonably could be expected to lead to an ASARCO
Takeover Proposal, or (ii) participate in any discussions or negotiations
regarding any ASARCO Takeover Proposal; provided, however, that if the ASARCO
Board determines in good faith, after consultation with outside counsel, that it
is necessary to do so in order to comply with its fiduciary duties to ASARCO's
shareholders under applicable law, ASARCO may, in response to an ASARCO Takeover
Proposal which was not

                                       11
<PAGE>
solicited by it or which did not otherwise result from a breach of the No
Solicitation Provision, and subject to providing the ASARCO Notice (x) furnish
information with respect to ASARCO and its subsidiaries to any person making an
ASARCO Takeover Proposal pursuant to a customary confidentiality agreement (as
determined by ASARCO after consultation with its outside counsel) and (y)
participate in discussions or negotiations regarding such ASARCO Takeover
Proposal. The No Solicitation Provision further provides that neither the ASARCO
Board nor any committee thereof shall (i) withdraw or modify, or propose
publicly to withdraw or modify, in a manner adverse to Phelps Dodge, the
recommendation by such Board of Directors of such committee of the Proposed PD
Merger or the PD Merger Agreement, (ii) approve or recommend, or propose
publicly to approve or recommend, any ASARCO Takeover Proposal, or (iii) cause
ASARCO to enter into an ASARCO Acquisition Agreement. Notwithstanding the
foregoing, in the event that the ASARCO Board receives an ASARCO Takeover
Proposal and the ASARCO Board determines in good faith, after consultation with
outside counsel, that it is necessary to do so in order to comply with its
fiduciary duties to ASARCO's shareholders under applicable law, the ASARCO Board
may (x) take any of the actions described in clauses (i), (ii) or (iii) of the
preceding sentence or (y) terminate the PD Merger Agreement (and concurrently
with or after such termination, if it so chooses, cause ASARCO to enter into any
ASARCO Acquisition Agreement with respect to any ASARCO Takeover Proposal) but
only after the fifth business day following Phelps Dodge's receipt of written
notice advising Phelps Dodge that the ASARCO Board is prepared to accept an
ASARCO Takeover Proposal, specifying the material terms and conditions of such
ASARCO Takeover Proposal and identifying the person making such ASARCO Takeover
Proposal.

    The PD Merger Agreement also provides that ASARCO shall be liable to Phelps
Dodge for the ASARCO Termination Fee payable by wire transfer of same day funds
if (i) prior to the meeting of ASARCO shareholders to consider and vote upon the
Proposed PD Merger an ASARCO Takeover Proposal shall have been made known to
ASARCO or shall have been made directly to its shareholders generally or any
person shall have publicly announced an intention (whether or not conditional)
to make an ASARCO Takeover Proposal and thereafter the PD Merger Agreement is
terminated by either Phelps Dodge or ASARCO in the event shares of Common Stock
are not purchased pursuant to the Phelps Dodge Exchange Offer for the Common
Stock on or before March 31, 2000 or (ii) the PD Merger Agreement is terminated
by ASARCO in order to enter into an agreement to accept an ASARCO Takeover
Proposal; provided, however, that no ASARCO Termination Fee shall be payable to
Phelps Dodge unless and until within 18 months of such termination ASARCO or any
of its subsidiaries enters into any ASARCO Acquisition Agreement or consummates
any ASARCO Takeover Proposal.

    Also on October 6, 1999, Parent and Purchaser received notice that they had
been granted early termination of the waiting period under the HSR Act. Later in
the evening of October 6, 1999, Mr. Larrea corresponded to Mr. McAllister to
register again his displeasure with the process employed by ASARCO in its
"auction."

    On October 7, 1999, Parent submitted to the ASARCO Board a letter detailing
the revised proposal to acquire ASARCO by Parent and Purchaser at the increased
Offer Price of $29.50 per share in cash. Subsequently, Parent issued the
following press release disclosing the delivery and contents of the letter:

                         GRUPO MEXICO INCREASES TENDER OFFER
                                TO ACQUIRE ASARCO INC.
                             TO $29.50 PER SHARE IN CASH
            RECEIVES EARLY TERMINATION TO HART-SCOTT-RODINO WAITING PERIOD

          MEXICO CITY (OCTOBER 7, 1999)--Grupo Mexico, S.A. de C.V., announced
      today that it has revised its proposal to acquire all of the outstanding
      shares of ASARCO Incorporated (NYSE:AR) to increase the price to $29.50
      per share in cash. The revised offer, which values

                                       12
<PAGE>
      ASARCO at $2.24 billion (including assumption of debt) is scheduled to
      expire at 12:00 midnight, New York City time, on Monday, October 25, 1999,
      unless extended.

          Following the completion of the tender offer, Grupo Mexico intends to
      consummate a second step merger in which all remaining ASARCO shareholders
      will also receive the same cash price paid in the tender offer.

          Earlier today, Grupo Mexico sent the following letter to the Board of
      Directors of ASARCO:

                                                                 October 7, 1999

      Board of Directors
      ASARCO Incorporated
      180 Maiden Lane
      New York, NY 10038

      Attention: Francis R. McAllister
      Chairman and Chief Executive Officer

      Dear Members of the Board:

          Based on our assessment of the pending offer by Phelps Dodge
      Corporation as reflected in your announced agreement with them, and our
      view of the intrinsic value in ASARCO Incorporated that Grupo Mexico, S.A.
      de C.V., could realize if Grupo Mexico owned ASARCO, we are today
      increasing the price in our September 27 tender offer to ASARCO
      shareholders for all outstanding shares of ASARCO to $29.50 per share in
      cash. The other terms of our September 27 tender offer remain
      substantially unchanged.

          Our revised offer provides value to your shareholders that is
      demonstrably superior to your agreement with Phelps Dodge. This offer
      represents a premium of 5% over the value of your recently announced
      agreement with Phelps Dodge based upon the October 6, 1999 closing price
      of $53.00 per share for Phelps Dodge common stock, and a premium of 59%
      over ASARCO's unaffected stock price on August 20, 1999, immediately prior
      to the announcement of Phelps Dodge's proposal.

          As a result, we believe that you can, and indeed are obligated to,
      meet with us and discuss our revised offer. Accordingly, we request that,
      pursuant to Section 5.9 of your agreement with Phelps Dodge, you elicit
      such advice and make such determinations in view of your fiduciary duties
      so that ASARCO would be in a position to immediately engage in
      negotiations and discussions with us concerning our superior proposal. We
      also believe that you cannot, consistent with your fiduciary duties,
      continue to recommend to your shareholders the transaction with Phelps
      Dodge in light of our revised offer.

          As before, our execution of a merger agreement would not be contingent
      upon a due diligence review. Furthermore, in view of the fact that we have
      been granted "early termination" of the waiting period under the
      Hart-Scott-Rodino Antitrust Improvements Act, we are confident that
      consummation of our proposed transaction is not subject to any material
      regulatory approvals.

          Our revised offer represents a compelling opportunity for ASARCO and
      its shareholders to improve upon your existing transaction with Phelps
      Dodge.

          Our offer, of course, continues to be conditioned upon entering into a
      negotiated agreement with you. As in the past, we are prepared to meet
      with you at any time to negotiate the terms of a merger agreement having
      substantially the same terms and conditions that were contained in the
      form of merger agreement that was submitted to you on October 5, 1999,
      modified to (i) remove

                                       13
<PAGE>
      our request for the "match" right in connection with competing proposals
      set forth in the "no-shop" provision and replacing it with the relevant
      provision in your Phelps Dodge Agreement, (ii) reflect the termination of
      your agreement with Phelps Dodge and (iii) incorporate certain provisions
      from your agreement with Phelps Dodge, provided that you enter into an
      agreement with us on or before October 15, 1999.

          Please contact us to schedule a meeting of our respective advisors to
      bring this situation to a prompt and satisfactory conclusion for the
      shareholders of both of our companies.

                                        Very truly yours,

                                        GRUPO MEXICO, S.A. de C.V.

                                        By  /s/ Daniel Tellechea Salido
       -------------------------------------------------------------------------
                                            Daniel Tellechea Salido
                                            Managing Director for Administration
                                            and Finance and Alternate Director

                                        By  /s/ Gerard Guerrero Diaz Mercado
       -------------------------------------------------------------------------
                                            Gerard Guerrero Diaz Mercado
                                            Treasurer

      cc: J. Michael Schill, Esq.

         Steven Koch

      Grupo Mexico is a diversified mining company that ranks among the world's
      largest copper, zinc and silver producers. The company's business includes
      mining, smelting and refining in Mexico and is one of the world's
      lowest-cost operations. Grupo Mexico also operates the largest railroad
      system in Mexico.

      NOTE: Statements in this press release include "forward-looking
      statements" that express expectations of future events or results. All
      statements based on future expectations rather than on historical facts
      are forward-looking statements that involve a number of risks and
      uncertainties, and the company cannot give assurance that such statements
      will prove to be correct.

                 6. CONDITIONS OF THE OFFER. The discussion set forth in the
             Introduction to the Offer to Purchase and Section 14 of the Offer
             to Purchase is amended and supplemented as follows:

                 A. The Minimum Condition is amended and restated to read as
             follows:

                 THE MINIMUM CONDITION.  CONSUMMATION OF THE OFFER IS
             CONDITIONED UPON THERE BEING VALIDLY TENDERED AND NOT PROPERLY
             WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER THAT NUMBER OF
             SHARES OF COMMON STOCK WHICH, TOGETHER WITH SHARES OF COMMON STOCK
             OWNED BY PARENT, CONSTITIUTE AT LEAST 80% OF THE SHARES OF COMMON
             STOCK OUTSTANDING ON A FULLY DILUTED BASIS (I.E., AS THOUGH ALL
             OPTIONS OR OTHER SECURITIES CONVERTIBLE INTO OR EXERCISABLE OR
             EXCHANGEABLE FOR COMMON STOCK HAD BEEN SO CONVERTED, EXERCISED OR
             EXCHANGED) (THE "MINIMUM CONDITON").

                 According to the schedules accompanying the revised form of
             merger agreement delivered by ASARCO to Parent's legal advisors on
             Monday, October 4, 1999, as of

                                       14
<PAGE>
             September 30, 1999 there were 39,921,427 shares of Common Stock
             outstanding and 1,799,669 Incentive Shares subject to issuance.

                 Parent currently owns an aggregate of 3,900,000 shares of
             Common Stock, which were acquired in open-market transactions.
             Accordingly, Purchaser believes that the Minimum Condition would be
             satisfied if an aggregate of 29,476,877 shares of Common Stock are
             validly tendered pursuant to the Offer. For purposes of the Offer,
             "fully diluted basis" assumes (i) no dilution due to Rights, (ii)
             the issuance of all of the Incentive Shares, (iii) no shares of
             Common Stock were issued or acquired by ASARCO after September 30,
             1999 (other than Common Stock issued pursuant to clause (ii) above)
             and no options, warrants, rights or other securities convertible
             into or exercisable or exchangeable for shares of Common Stock were
             issued or granted after September 30, 1999, and (iv) as of
             September 30, 1999 ASARCO had no other obligations to issue Common
             Stock or other securities convertible into or exercisable for
             shares of Common Stock.

                 B. The Merger Agreement Condition is amended and restated to
             read as follows:

                 THE MERGER AGREEMENT CONDITION.  CONSUMMATION OF THE OFFER IS
             CONDITIONED UPON PURCHASER BEING SATISFIED, IN ITS SOLE DISCRETION,
             THAT THE PD MERGER AGREEMENT HAS BEEN TERMINATED AND ASARCO HAVING
             ENTERED INTO A DEFINITIVE MERGER AGREEMENT WITH PARENT AND
             PURCHASER THAT WOULD PROVIDE FOR THE ACQUISITION OF ASARCO BY
             PARENT OR PURCHASER ("THE MERGER AGREEMENT CONDITION").

                 In order for the Merger Agreement Condition to be satisfied,
             the PD Merger Agreement must be terminated. Depending on ASARCO's
             willingness to enter into negotiations with Parent and Purchaser
             and the then pending status of any such negotiations, Purchaser may
             extend the Offer from time to time until the Merger Agreement
             Condition is satisfied.

                 In the event the Merger Agreement condition is satisfied prior
             to 5:00 p.m. on October 15, 1999, Purchaser, under the terms of the
             Second Amended and Restated Commitment Letter, will be in the
             position to substantially limit its conditions to the following:

                     Notwithstanding any other provisions of the Offer, and in
                 addition to (and not in limitation of) the Purchaser's rights
                 to extend and amend the Offer at any time in its sole
                 discretion (subject to the provisions of the Agreement), the
                 Purchaser shall not be required to accept for payment or,
                 subject to any applicable rules and regulations of the SEC,
                 including Rule 14e-1(c) under the Exchange Act (relating to the
                 Purchaser's obligation to pay for or return tendered Common
                 Stock promptly after termination or withdrawal of the Offer),
                 pay for, and may delay the acceptance for payment of or,
                 subject to the restriction referred to above, the payment for,
                 any tendered shares of Common Stock, and may terminate or amend
                 the Offer (but only subject to and in accordance with the
                 agreement relating to the Proposed Merger) if (i) the Minimum
                 Condition has not been satisfied or (ii) before the time of
                 acceptance of shares of Common Stock for payment pursuant to
                 the Offer, any of the following events shall occur:

                     (a) there shall have been any statute, rule, regulation,
                 judgment, order or injunction promulgated, entered, enforced,
                 enacted, issued or rendered applicable to the Offer or the
                 Proposed Merger by any domestic or foreign, federal or state
                 governmental commission which (i) prohibits, or imposes any
                 material limitations on,

                                       15
<PAGE>
                 Parent's or the Purchaser's ownership or operation of all or a
                 material portion of ASARCO's businesses or assets, (ii)
                 prohibits, or makes illegal the acceptance for payment, payment
                 for or purchase of Common Stock or the consummation of the
                 Offer or the Proposed Merger, (iii) results in a material delay
                 in or restricts the ability of the Purchaser, or renders the
                 Purchaser unable, to accept for payment, pay for or purchase
                 some or all of the tendered shares of Common Stock, or (iv)
                 imposes material limitations on the ability of the Purchaser or
                 Parent effectively to exercise full rights of ownership of the
                 Common Stock, including, without limitation, the right to vote
                 the Common Stock purchased by it on all matters properly
                 presented to ASARCO's shareholders.

                     (b) the representations and warranties of ASARCO set forth
                 in the agreement relating to the Proposed Merger shall not be
                 true and correct as of the date of consummation of the Offer as
                 though made on or as of such date except, in each case, (A)
                 those representations and warranties that address matters only
                 as of a particular date which are true and correct as of such
                 date or (B) where the failure of such representations and
                 warranties to be true and correct (without giving effect to any
                 qualifications as to "materiality" or "Material Adverse Effect"
                 set forth therein), would not reasonably be expected to have,
                 individually or in the aggregate, a Material Adverse Effect on
                 ASARCO; or ASARCO shall have breached or failed in any material
                 respect to perform or comply with any material obligation,
                 agreement or covenant required by the Agreement to be performed
                 or complied with by it;

                     (c) the Agreement shall have been terminated in accordance
                 with its terms prior to the Expiration Date;

                     (d) ASARCO shall have entered into a definitive agreement
                 or agreement in principle with any person with respect to an
                 ASARCO Takeover Proposal or similar business combination with
                 ASARCO; or

                     (e) in the event the consummation of the Offer shall not
                 have occurred prior to the meeting of the ASARCO shareholders
                 to approve the Proposed Merger there having occurred (i) after
                 the date hereof to November 30, 1999, a general banking
                 moratorium established by Federal or state authorities, a
                 generally recognized capital markets crisis, as evidenced by a
                 cumulative 20% decline in the Dow Jones Industrial Average over
                 a period of five consecutive trading days, or a virtual
                 cessation in bank and other private debt financings or the
                 introduction of additional material government restrictions
                 imposed upon lending institutions which materially affect the
                 type of transactions contemplated thereby, and (ii) after
                 November 30, 1999, a material disruption of or material adverse
                 change in U.S. or developed country financial, banking or
                 capital market conditions that, in our judgment, is reasonably
                 likely to materially impair the syndication of the Facilities,

                     (f) the ASARCO Board shall have withdrawn, or amended,
                 modified or changed in a manner adverse to Parent or the
                 Purchaser (including by amendment of the ASARCO Schedule 14D-9
                 containing the ASARCO Board recommendation to accept the
                 Offer), its recommendation of the Offer, the Agreement or the
                 Proposed Merger, or recommended another proposal or offer from
                 any person other than Parent or the Purchaser, or shall have
                 resolved to do any of the foregoing;

             which in the reasonable judgment of Parent or the Purchaser, in any
             such case, and regardless of the circumstances giving rise to such
             condition, makes it inadvisable to proceed with the Offer and/or
             with such acceptance for payment or payments.

                                       16
<PAGE>
                 The foregoing conditions will be for the sole benefit of the
             Purchaser and Parent and may be waived by Parent or the Purchaser,
             in whole or in part at any time and from time to time, in the sole
             discretion of Parent or the Purchaser."

                 7. CERTAIN LEGAL MATTERS; REGULATORY APPROVALS; CERTAIN
             LITIGATION. The discussion set forth in Section 15 of the Offer to
             Purchase is amended and supplemented as follows:

                 U.S. ANTITRUST. As noted above, on October 6, 1999, Parent and
             Purchaser received notice that they had been granted early
             termination of the waiting period under the HSR Act. Accordingly,
             Parent is free to consummate the Offer and the Proposed Merger at
             any time without any further requirements under the HSR Act.

                 8. MISCELLANEOUS. The Schedule 14D-1, and any amendments
             thereto, may be inspected at, and copies may be obtained from, the
             same places and in the same manner as set forth in Section 8 of the
             Offer to Purchase (except that they may not be available at the
             regional offices of the SEC).

             ASMEX CORPORATION

             October 8, 1999

                                       17
<PAGE>
    Facsimile copies of the Letters of Transmittal, properly completed and duly
signed, will be accepted. The Letter of Transmittal, Common Stock Certificates
(and Rights Certificates, if applicable) and any other required documents should
be sent by each shareholder of ASARCO or his broker, dealer, commercial bank,
trust company or other nominee to the Depositary as follows:

                        THE DEPOSITARY FOR THE OFFER IS:

                                 CITIBANK, N.A.

<TABLE>
<S>                            <C>                            <C>
         BY COURIER:                     BY MAIL:                       BY HAND:

       Citibank, N.A.                 Citibank, N.A.                 Citibank, N.A.
        915 Broadway                   P.O. Box 685              Corporate Trust Window
          5th Floor                 Old Chelsea Station        111 Wall Street, 5th Floor
  New York, New York 10010       New York, New York 10113       New York, New York 10043
</TABLE>

              Facsimile for Eligible Institutions: (212) 505-2248

                   To Confirm Facsimile Only: (800) 270-0808

                              -------------------

    Any questions or requests for assistance may be directed to the Information
Agent or the Dealer
Manager at their respective telephone numbers and locations listed below.
Additional copies of the Offer to Purchase, this Supplement, the Letter of
Transmittal and the Notice of Guaranteed Delivery may be obtained from the
Information Agent at its address and telephone numbers set forth below. Holders
of share of Common Stock may also contact their broker, dealer, commercial bank
or trust company or other nominee for assistance concerning the Offer.

                    THE INFORMATION AGENT FOR THE OFFER IS:

                             D.F. KING & CO., INC.

                                 UNITED STATES
                                77 Water Street
                            New York, New York 10005
                         CALL TOLL-FREE: (800) 714-3305
                                       or
                         (212) 269-5550 (call collect)

                                     EUROPE
                        Royex House, Aldermanbury Square
                            London, England EC2V 7HR
                        (44) 171 600 5005 (call collect)

                      THE DEALER MANAGER FOR THE OFFER IS:

                             CHASE SECURITIES INC.

                                270 Park Avenue
                            New York, New York 10017
                           Telephone: (212) 270-3298



<PAGE>
                                                              Exhibit 99(a)(11)
                   GRUPO MEXICO INCREASES TENDER OFFER
                        TO ACQUIRE ASARCO INC.
                       TO $29.50 PER SHARE IN CASH

          RECEIVES EARLY TERMINATION TO HART-SCOTT-RODINO WAITING PERIOD

Mexico City (October 7, 1999) -- Grupo Mexico, S.A. de C.V., announced today
that it has revised its proposal to acquire all of the outstanding shares of
ASARCO Incorporated (NYSE:AR) to increase the price to $29.50 per share in
cash. The revised offer, which values ASARCO at $2.24 billion (including
assumption of debt), is scheduled to expire at 12:00 midnight, New York City
Time, on Monday, October 25, 1999, unless extended.

Following the completion of the tender offer, Grupo Mexico intends to
consummate a second step merger in which all remaining ASARCO shareholders
will also receive the same cash price paid in the tender offer.

Earlier today, Grupo Mexico sent the following letter to the Board of
Directors of ASARCO:

                                                                 October 7, 1999
Board of Directors
ASARCO Incorporated
180 Maiden Lane
New York, NY 10038

Attention: Francis R. McAllister
Chairman and Chief Executive Officer

Dear Members of the Board:

         Based on our assessment of the pending offer by Phelps Dodge
Corporation as reflected in your announced agreement with them, and our view of
the intrinsic value in ASARCO Incorporated that Grupo Mexico, S.A. de C.V.,
could realize if Grupo Mexico owned ASARCO, we are today increasing the price in
our September 27 tender offer to ASARCO shareholders for all outstanding shares
of ASARCO to $29.50 per share in cash. The other terms of our September 27
tender offer remain substantially unchanged.

         Our revised offer provides value to your shareholders that is
demonstrably superior to your agreement with Phelps Dodge. This offer
represents a premium of 5% over the value of your recently announced
agreement with Phelps Dodge based upon the October 6, 1999 closing price of
$53.00 per share for Phelps Dodge common stock, and a premium of 59% over
ASARCO's unaffected stock price on August 20, 1999, immediately prior to the
announcement of Phelps Dodge's proposal.

         As a result, we believe that you can, and indeed are obligated to,
meet with us and discuss our revised offer. Accordingly, we request that,
pursuant to Section 5.9 of your agreement with Phelps Dodge, you elicit such
advice and make such determinations in view of your fiduciary duties so
that ASARCO would be in a position to immediately engage in negotiations and
discussions with us concerning our superior proposal. We also believe that
you cannot, consistent with your fiduciary duties, continue to recommend to
your shareholders the transaction with Phelps Dodge in light of our revised
offer.

         As before, our execution of a merger agreement would not be
contingent upon a due diligence review. Furthermore, in view of the fact that
we have been granted "early termination" of the waiting period under the
Hart-Scott-Rodino Antitrust Improvements Act, we are confident that
consummation of our proposed transaction is not subject to any material
regulatory approvals.

         Our revised offer presents a compelling opportunity for ASARCO and
its shareholders to improve upon your existing transaction with Phelps Dodge.

         Our offer, of course, continues to be conditioned upon entering into
a negotiated agreement with you. As in the past, we are prepared to meet with
you at any time to negotiate the terms of a merger agreement having
substantially the same terms and conditions that were contained in the form
of merger agreement that was submitted to you on October 5, 1999, modified to
(i) remove our request for the "match" right in connection with competing
proposals set forth in the "no-

                                         1

<PAGE>

shop" provision and replacing it with the relevant provision in your Phelps
Dodge agreement, (ii) reflect the termination of your agreement with Phelps
Dodge and (iii) incorporate certain provisions from your agreement with Phelps
Dodge, provided that you enter into an agreement with us on or before October
15, 1999.

         Please contact us to schedule a meeting of our respective
advisors to bring this situation to a prompt and satisfactory conclusion for the
shareholders of both of our companies.

                                         Very truly yours,

                                         GRUPO MEXICO, S.A. de C.V.


                                         By /s/ Daniel Tellechea Salido
                                            -----------------------------------
                                              Daniel Tellechea Salido
                                              Managing Director for
                                              Administration and Finance and
                                              Alternative Director


                                         By /s/ Genaro Guerrero Diaz Mercado
                                            -----------------------------------
                                              Genaro Guerrero Diaz Mercado
                                              Treasurer

cc  J. Michael Schell, Esq.
    Steven Koch

Grupo Mexico is a diversified mining company that ranks among the world's
largest copper, zinc and silver producers. The company's business includes
mining, smelting and refining in Mexico and is one of the world's lowest-cost
operations. Grupo Mexico also operates the largest railroad system in Mexico.

NOTE: Statements in this press release include "forward-looking statements" that
express expectations of future events or results. All statements based on future
expectations rather than on historical facts are forward-looking statements that
involve a number of risks and uncertainties, and the company cannot give
assurance that such statements will prove to be correct.


                                         2

<PAGE>
                                                                Exhibit 99(b)(2)

[LOGO]


THE CHASE MANHATTAN BANK                                   CHASE SECURITIES INC.
270 Park Avenue                                                  270 Park Avenue
New York, New York  10017                              New York, New York  10017



                                              October 5, 1999


                                ASMEX Corporation
                        Senior Secured Credit Facilities
                     Amended and Restated Commitment Letter

Grupo Mexico, S.A. de C.V.
Baja California 200
Colonia Roma Sur
Mexico, D.F.  Mexico
06760

Attention:  Daniel Tellechea

Ladies and Gentlemen:

     This Amended and Restated Commitment Letter hereby, subject to the terms
and conditions set forth herein, amends and restates the Commitment Letter dated
September 24, 1999 (the "ORIGINAL COMMITMENT"), among Grupo Mexico, Chase and
CSI (each as defined below). You have advised The Chase Manhattan Bank ("Chase")
and Chase Securities Inc. ("CSI") that ASMEX Corporation, a Delaware corporation
(the "BORROWER"), a wholly-owned subsidiary of Grupo Mexico, S.A. de C.V., a
Mexican corporation ("GRUPO MEXICO"), intends to make a cash tender offer (the
"TENDER OFFER") for common stock of Asarco Incorporated, a New Jersey
corporation ("ASARCO"), representing at least 80% of the ordinary voting power
of all of the shares of capital stock of Asarco on a fully diluted basis
(including stock of Asarco owned by

- --------------------------------------------------------------------------------
[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.

<PAGE>
                                       2


Grupo Mexico and subsidiaries prior to the Tender Offer), to be followed by the
merger of the Borrower into Asarco, with Asarco thereby becoming a wholly-owned
subsidiary of Grupo Mexico.

         We understand that to provide funds for the Tender Offer and to pay
related fees and expenses, Grupo Mexico requires that senior secured financing
be made available to the Borrower in the amount of up to $823 million (the "A
TENDER FACILITY"). We further understand that, following the successful
completion of the Tender Offer, the Borrower is to be merged into Asarco with
Asarco thereby becoming a wholly-owned subsidiary of Grupo Mexico (the "MERGER"
and, together with the Tender Offer, the "Transactions"), and that (whether or
not the Merger is immediately effected) Grupo Mexico will require senior
financing for Asarco (the "R/C FACILITIES") in an aggregate amount equal to $250
million in order to refinance certain indebtedness of Asarco and to provide
funds for ongoing general corporate purposes. The A Tender Facility and the R/C
Facilities are herein collectively referred to as the "FACILITIES".

         In that connection, you have requested that CSI agree to structure,
arrange and syndicate the Facilities, and that Chase commit to provide the
entire principal amount of the Facilities and to serve as administrative agent
for the Facilities.

         CSI is pleased to advise you that it is willing to act as exclusive
advisor, lead arranger and book manager for the Facilities.

         Furthermore, Chase is pleased to advise you of its commitment to
provide the entire amount of the Facilities upon the terms and subject to the
conditions set forth or referred to in this amended and restated commitment
letter (the "AMENDED AND RESTATED COMMITMENT LETTER"), in the Amended and
Restated Summary of Terms and Conditions attached hereto as Exhibit A (the "TERM
SHEET") and in the Fee Letter dated September 24, 1999 (the "FEE LETTER"). We
intend to syndicate the Facilities to a group of financial institutions
(together with Chase, the "LENDERS") identified by us in consultation with you.
Chase shall be relieved of its obligation to provide the entire amount of the
Facilities to the extent that the offers of Lenders other than Chase to provide
any portion of the Facilities are accepted.

         CSI intends to commence syndication efforts promptly, and you agree
actively to assist CSI in its efforts to complete a syndication satisfactory to
it prior to the Tender Closing Date referred to in the Term Sheet. Such
assistance shall include (a) your using commercially reasonable efforts to
ensure that the syndication efforts benefit materially from your existing
lending relationships, (b) direct contact between senior management and advisors
of yourselves and the Borrower and the proposed Lenders, (c) assistance in the
preparation of a Confidential Information Memorandum and other marketing
materials to be used in connection with the syndication and (d) the hosting,
with CSI, of one or more meetings of prospective Lenders.

         It is agreed that Chase will act as the sole and exclusive
Administrative Agent for the Facilities and as the Collateral Agent in
connection with the Facilities, and that CSI will act as the sole and exclusive
advisor, arranger and book manager for the Facilities, and each will, in such
capacities, perform the duties and exercise the authority customarily performed
and exercised by it in such roles. You agree that no other agents, co-agents,
arrangers or book

- --------------------------------------------------------------------------------
[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       3


managers will be appointed, no other titles will be awarded and no compensation
(other than that expressly contemplated by the Term Sheet and the Fee Letter
referred to below) will be paid in connection with the Facilities unless you and
we shall so agree.

         CSI will (in consultation with you) manage all aspects of the
syndication, including decisions as to the selection of institutions to be
approached and when they will be approached, when their commitments will be
accepted, which institutions will participate, the allocations of the
commitments among the Lenders and the amount and distribution of fees among the
Lenders. To assist CSI in its syndication efforts, you agree promptly to prepare
and provide to CSI and Chase all information with respect to Grupo Mexico, Grupo
Minero Mexico, S.A. de C.V., a Mexican corporation ("GMM") , the Borrower and
their respective subsidiaries, the Transactions and the other matters
contemplated hereby, including all financial information and projections (the
"PROJECTIONS"), as we may reasonably request in connection with the arrangement
and syndication of the Facilities. You hereby represent and covenant that (a)
all information other than the Projections (the "INFORMATION") that has been or
will be made available to Chase or CSI by you or any of your representatives is
or will be, when furnished, complete and correct in all material respects and
does not or will not, when furnished, contain any untrue statement of a material
fact or omit to state a material fact necessary in order to make the statements
contained therein not materially misleading in light of the circumstances under
which such statements are made and (b) the Projections that have been or will be
made available to Chase or CSI by you or any of your representatives have been
or will be prepared in good faith based upon reasonable assumptions. You
understand that in arranging and syndicating the Facilities we may use and rely
on the Information and Projections without independent verification thereof.

         As consideration for Chase's commitment hereunder and CSI's agreement
to perform the services described herein, you agree to pay and to cause the
Borrower to pay to Chase the non-refundable fees set forth in Annex I to the
Term Sheet and in the Fee Letter.

         Chase's commitment hereunder and CSI's agreement to perform the
services described herein are subject to

                  (a) (i) there not occurring or becoming known to us any
         material adverse condition or material adverse change in or affecting
         the business, operations, property or financial condition of Grupo
         Mexico and its subsidiaries, GMM and its subsidiaries, or Asarco and
         its subsidiaries, in each case taken as a whole, which (in the case of
         Asarco and its subsidiaries) is not already disclosed and publicly
         available or otherwise known by any of our officers who is working with
         you on the Transactions; PROVIDED, HOWEVER, that any adverse effect
         that copper prices have had or may have on the business, operations,
         property or financial condition of Grupo Mexico and its subsidiaries,
         GMM and its subsidiaries, or Asarco and its subsidiaries, in each case
         taken as a whole, shall not be deemed to be such a material adverse
         condition or material adverse change for purposes of this clause
         (a)(i); and (ii) our not becoming aware after September 24, 1999, of
         any information or other matter affecting Grupo Mexico and its
         subsidiaries, GMM and its subsidiaries, Asarco and its subsidiaries, in
         each case taken as a whole, or the

- --------------------------------------------------------------------------------
[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       4


         transactions contemplated hereby which is inconsistent in a material
         and adverse manner with any such information or other matter disclosed
         to us prior to September 24, 1999, and which (in the case of Asarco and
         its subsidiaries) is not already disclosed and publicly available or
         otherwise known by any of our officers who is working with you on the
         Transactions,

                  (b) there shall not have been any statute, rule, regulation,
         judgment, order or injunction promulgated, entered, enforced, enacted,
         issued or applicable to the Tender Offer or the Merger by any domestic
         or foreign federal or state governmental regulatory or administrative
         agency or authority or court or legislative body or commission which
         (i) prohibits, or imposes any material limitations on, Grupo Mexico's
         or Asmex' ownership or operation of all or a material portion of
         Asarco's businesses or assets, (ii) prohibits, or makes illegal the
         acceptance for payment, payment for or purchase of Asarco common stock
         or the consummation of the Tender Offer or the Merger, (iii) results in
         a material delay in or restricts the ability of Grupo Mexico, or
         renders Grupo Mexico unable, to accept for payment, pay for or purchase
         some or all of the tendered shares of Asarco common stock, or (iv)
         imposes material limitations on the ability of Asmex or Grupo Mexico
         effectively to exercise full rights of ownership of the Asarco common
         stock, including, without limitation, the right to vote the Asarco
         common stock purchased by it on all matters properly presented to
         Asarco's shareholders,

                  (c) there not having occurred (i) after the date hereof to
         November 30, 1999, a general banking moratorium established by Federal
         or state authorities, a generally recognized capital markets crisis, as
         evidenced by a cumulative 20% decline in the Dow Jones Industrial
         Average over a period of five (5) consecutive trading days, or a
         virtual cessation in bank and other private debt financings or the
         introduction of additional material government restrictions imposed
         upon lending institutions which materially affect the type of
         transactions contemplated thereby, and (ii) after November 30, 1999, a
         material disruption of or material adverse change in U.S. or developed
         country financial, banking or capital market conditions that, in our
         judgment, is reasonably likely to materially impair the syndication of
         the Facilities,

                  (d) our satisfaction that prior to and during the syndication
         of the Facilities there shall be no competing offering, placement or
         arrangement of any debt securities or bank financing by or on behalf of
         Grupo Mexico or any affiliate thereof,

                  (e) in the case of the A Tender Facility, our satisfaction
         with the conditions of the Tender Offer which will include, in any
         event (unless otherwise satisfied in connection with the definitive
         Merger agreement with Asarco), (i) invalidation, redemption or other
         inapplicability of the rights issued under Asarco's Shareholder Rights
         Agreement dated as of January 28, 1998, as amended, (ii) invalidation
         or satisfaction of the requirements of Article 7 of Asarco's Restated
         Certificate of Incorporation with respect to the Transactions such that
         following consummation of the Tender Offer the Merger may be
         consummated without the affirmative vote of the holders of any Asarco
         shares other than the Borrower, (iii) invalidity, inapplicability or
         satisfaction (if necessary) of Article 10 of

- --------------------------------------------------------------------------------
[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       5


         Asarco's Restated Certificate of Incorporation with respect to the
         Transactions or the Facilities, (iv) satisfaction or inapplicability of
         the requirements of Section 14A:10A of the New Jersey Business
         Corporation Act with respect to the Merger such that following
         consummation of the Tender Offer the Merger may be consummated without
         the affirmative vote of the holders of any Asarco shares other than the
         Borrower and (v) obtaining all regulatory approvals and consents
         (including Hart-Scott-Rodino and other approvals or consents, if any)
         necessary to effect the Transactions,

                  (f) in the case of the R/C Facilities, prior or concurrent
         disbursement of the A Tender Facility, successful consummation of the
         Tender Offer and our satisfaction with the terms and conditions of the
         definitive Merger agreement,

                  (g) the negotiation, execution and delivery on or prior to the
         Tender Closing Date of definitive documentation with respect to the
         Facilities satisfactory to all parties, and

                  (h) the other conditions set forth or referred to in the Term
         Sheet.

The terms and conditions of Chase's commitments hereunder and of the Facilities
are not limited to those set forth herein and in the Term Sheet and Fee Letter.
Those matters that are not covered by the provisions hereof and of the Term
Sheet are subject to the approval and agreement of Chase, CSI and Grupo Mexico.
Notwithstanding the foregoing, the Term Sheet and Fee Letter are intended to
reflect all material closing conditions, representations and warranties,
covenants and events of default, subject however, in each case, to such
additional provisions as shall be appropriate to take into account developments
after September 24, 1999.

         You agree (a) to indemnify and hold harmless Chase, CSI, their
affiliates and their respective officers, directors, employees, advisors, and
agents (each, an "INDEMNIFIED PERSON") from and against any and all losses,
claims, damages and liabilities to which any such indemnified person may become
subject arising out of or in connection with this Amended and Restated
Commitment Letter, the Facilities, the use of the proceeds thereof, the
Transactions or any related transaction or any claim, litigation, investigation
or proceeding relating to any of the foregoing, regardless of whether any
indemnified person is a party thereto, and to reimburse each indemnified person
upon demand for any legal or other expenses incurred in connection with
investigating or defending any of the foregoing, PROVIDED that the foregoing
indemnity will not, as to any indemnified person, apply to losses, claims,
damages, liabilities or related expenses to the extent they are found by a
final, non-appealable judgment of a court to arise from the willful misconduct
or gross negligence of such indemnified person, and (b) to reimburse Chase, CSI
and their affiliates on demand for all reasonable and documented out-of-pocket
expenses (including due diligence expenses, syndication expenses, consultant's
fees and expenses, travel expenses, and reasonable fees, charges and
disbursements of counsel) incurred in connection with the Facilities and any
related documentation (including this Amended and Restated Commitment Letter,
the Term Sheet, the Fee Letter and the definitive financing documentation) or
(without duplication of fees or costs for administrative services covered in the
Fee Letter) the administration, amendment, modification or waiver thereof. No
indemnified person shall be liable for any damages arising from the use by
others of Information or other materials obtained

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       6


through electronic, telecommunications or other information transmission
systems, or for any special, indirect, consequential or punitive damages in
connection with the Facilities.

         You acknowledge that Chase and/or CSI may be providing debt financing,
equity capital or other services (including financial advisory services) to
other companies in respect of which you may have conflicting interests regarding
the transactions described hereby and otherwise. Neither Chase nor CSI will use
confidential information obtained from you by virtue of the transactions
contemplated hereby or other relationships with you in connection with the
performance by Chase or CSI of services for other companies, and neither Chase
nor CSI will furnish any such information to other companies. You also
acknowledge that neither Chase nor CSI has any obligation to use in connection
with the transactions contemplated hereby, or to furnish to you, confidential
information obtained from other companies.

         This Amended and Restated Commitment Letter shall not be assignable by
you without the prior written consent of Chase and CSI (and any purported
assignment without such consent shall be null and void), is intended to be
solely for the benefit of the parties hereto and is not intended to confer any
benefits upon, or create any rights in favor of, any person other than the
parties hereto. This Amended and Restated Commitment Letter may not be amended
or waived except by an instrument in writing signed by you, Chase and CSI. This
Amended and Restated Commitment Letter may be executed in any number of
counterparts, each of which shall be an original, and all of which, when taken
together, shall constitute one agreement. Delivery of an executed signature page
of this Amended and Restated Commitment Letter by facsimile transmission shall
be effective as delivery of a manually executed counterpart hereof. This Amended
and Restated Commitment Letter and the Fee Letter set forth the entire
understanding of the parties with respect thereto. This Amended and Restated
Commitment Letter shall be governed by, and construed in accordance with, the
laws of the State of New York.

         This Amended and Restated Commitment Letter is delivered to you on the
understanding that neither this Amended and Restated Commitment Letter, the Term
Sheet or the Fee Letter nor any of their terms or substance shall be disclosed,
directly or indirectly, to any other person except (a) to your officers, agents
and advisors who are directly involved in the consideration of this matter or
(b) as may be compelled in a judicial or administrative proceeding or as
otherwise required by law (in which case you agree to inform us promptly
thereof), PROVIDED, that the foregoing restrictions shall cease to apply (except
in respect of the Fee Letter and its terms and substance) after this Amended and
Restated Commitment Letter has been accepted by you.

         The compensation, reimbursement, indemnification and confidentiality
provisions contained herein and in the Fee Letter shall remain in full force and
effect regardless of whether definitive financing documentation shall be
executed and delivered and notwithstanding the termination of this Amended and
Restated Commitment Letter or Chase's commitments hereunder.

         If the foregoing correctly sets forth our agreement, please indicate
your acceptance of the terms hereof and of the Term Sheet by returning to us
executed counterparts

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       7


hereof not later than 6:00 p.m., New York City time, on October 5, 1999 (at
which time this Amended and Restated Commitment Letter shall expire if not
executed and delivered by you). Further, this Amended and Restated Commitment
Letter and the amendments of the Original Commitment and the Summary of Terms
and Conditions attached thereto as Exhibit A set forth herein and in the Term
Sheet shall not become effective UNLESS Grupo Mexico and Asarco execute and
deliver a definitive Merger agreement satisfactory to Chase and CSI, not later
than 5:00 p.m., New York City time, on October 8, 1999.


































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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       8


         Chase and CSI are pleased to have been given the opportunity to assist
you in connection with this important financing.

         Upon the effectiveness of this Amended and Restated Commitment Letter,
references in the Fee Letter to the "Commitment Letter" (other than the
reference thereto in clause (i) of the second paragraph of the Fee Letter) shall
mean the Original Commitment, as amended and restated hereby. Except as set
forth in the preceding sentence, the Fee Letter shall remain unmodified and in
full force and effect.

                                      Very truly yours,

                                      THE CHASE MANHATTAN BANK



                                      By: /s/ Deborah Davey
                                         ---------------------------------------
                                         Name:  Deborah Davey
                                         Title: Vice President

                                      CHASE SECURITIES INC.



                                      By: /s/ Christopher I. Teague
                                         ---------------------------------------
                                         Name:  Christopher I. Teague
                                         Title: Managing Director



Accepted and agreed to as of the
date first written above by:

GRUPO MEXICO, S.A. DE C.V.



By: /s/ Daniel Tellechea Salido
   ----------------------------------
   Name:  Daniel Tellechea Salido
   Title: Managing Director For
          Administration and Finance

By: /s/ Genaro Guerrero Diaz Mercado
   ------------------------------------
   Name:  Genaro Guerrero Diaz Mercado
   Title: Treasurer


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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.

<PAGE>
                                                                       Exhibit A



                        SENIOR SECURED CREDIT FACILITIES
              Amended and Restated Summary of Terms and Conditions

                                 October 5, 1999

         AS USED HEREIN, CAPITALIZED TERMS NOT OTHERWISE DEFINED HEREIN SHALL
HAVE THE RESPECTIVE MEANINGS ASCRIBED TO THEM IN THE AMENDED AND RESTATED
COMMITMENT LETTER TO WHICH THIS AMENDED AND RESTATED SUMMARY OF TERMS AND
CONDITIONS IS ATTACHED.

         This Amended and Restated Summary of Terms and Conditions hereby,
subject to the terms and conditions set forth in the Amended and Restated
Commitment Letter, amends and restates the Summary of Terms and Conditions dated
September 24, 1999. The following sets forth the terms and conditions for the
senior secured credit facilities that will be made available to ASMEX
Corporation, a Delaware corporation ("ASMEX"), in connection with Asmex'
proposed cash tender offer (the "TENDER OFFER" and, together with the Merger
defined below, the "TRANSACTIONS") for shares of common stock of Asarco
Incorporated (the "SHARES"), a New Jersey corporation ("ASARCO"), representing
not less than 80% of the ordinary voting power of all of the shares of capital
stock of Asarco on a fully diluted basis, including stock of Asarco owned by
Grupo Mexico, S.A. de C.V., ("GRUPO MEXICO") and subsidiaries prior to the
Tender Offer (determined in a manner satisfactory to the Arranger). The
conditions precedent to the obligation of Asmex to purchase the Shares pursuant
to the Tender Offer will include, unless otherwise satisfied in connection with
the definitive Merger agreement with Asarco, the following: (i) invalidation,
redemption or other inapplicability of the rights issued under Asarco's
Shareholder Rights Agreement dated as of January 28, 1998, as amended, (ii)
invalidation or satisfaction of the requirements of Article 7 of Asarco's
Restated Certificate of Incorporation with respect to the Transactions such
that, following consummation of the Tender Offer, the Merger can be consummated
without the affirmative vote of the holders of any Asarco shares other than
Asmex, (iii) invalidity, inapplicability or satisfaction (if necessary) of
Article 10 of Asarco's Restated Certificate of Incorporation with respect to the
Transactions or the Facilities, (iv) satisfaction or inapplicability of the
requirements of Section 14A:10A of the New Jersey Business Corporation Act with
respect to the Merger such that following consummation of the Tender Offer the
Merger can be consummated without the affirmative vote of the holders of any
Asarco shares other than Asmex and (v) obtaining all regulatory approvals and
consents (including Hart-Scott-Rodino, and other approvals or consents, if any)
necessary to effect the Transactions. The purchase of shares will be funded
through credit facilities (the "A Tender Facility" referred to below) together
with certain cash from Grupo Minero Mexico, S.A. de C.V. ("GMM") and Grupo
Mexico. Following the purchase of the Shares pursuant to the Tender Offer,
Asmex, a direct wholly-owned subsidiary of Grupo Mexico, is to be merged into
Asarco with Asarco thereby becoming a wholly-owned subsidiary of Grupo Mexico
and with Asarco shareholders receiving solely cash consideration (the "MERGER").
The following also sets forth the terms and conditions for the other senior
credit facilities (the "R/C Facilities" referred to below) that will be made
available to Asarco upon and subsequent to consummation of the Tender Offer.

<PAGE>
                                       2


I.       PARTIES

         Borrowers:                 Under the A Tender Facility, ASMEX
                                    Corporation ("ASMEX") and, after the Merger,
                                    Asarco; and under the R/C Facilities, Asarco
                                    (each of Asmex and Asarco being sometimes
                                    referred to below as a "BORROWER").

         Guarantor(s):              Under the A Tender Facility, Grupo Mexico;
                                    and under the R/C Facilities, Grupo Mexico
                                    and, until consummation of the Merger,
                                    Asmex.

         Advisor, Lead Arranger
         and Book Manager:          Chase Securities Inc. (in such capacity, the
                                    "ARRANGER").

         Administrative Agent:      The Chase Manhattan Bank ("CHASE" and, in
                                    such capacity, the "ADMINISTRATIVE AGENT").

         Lenders:                   A syndicate of banks, financial institutions
                                    and other entities, including Chase,
                                    arranged by the Arranger in consultation
                                    with Grupo Mexico (collectively, the
                                    "LENDERS").

II.      TYPES AND AMOUNTS OF
         CREDIT FACILITIES

         1.  A TENDER FACILITY

             Type and Amount of
              Facility:             An aggregate principal amount of up to $823
                                    million will be available to Asmex under a
                                    senior secured credit facility (the "A
                                    TENDER FACILITY").

             Availability:          The Loans under the A Tender Facility (the
                                    "A TENDER LOANS") shall be made in a single
                                    drawing on the Tender Closing Date (as
                                    defined below); provided that in the event
                                    of tender of less than 100% of the Shares of
                                    Asarco (other than those owned by Grupo
                                    Mexico and subsidiaries) in the Tender
                                    Offer, the unused portion of the commitments
                                    under the A Tender Facility

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       3


                                    will be reserved for drawing on the Merger
                                    closing date for payment for the remaining
                                    Shares of Asarco.

              Amortization:         The A Tender Loans shall be repayable in
                                    full on the date eighteen (18) months after
                                    the Tender Closing Date (the date on which
                                    the A Tender Loans are repayable, the
                                    "MATURITY DATE").

              Purpose:              The proceeds of the A Tender Loans shall be
                                    used to purchase Shares.

         2.   R/C FACILITIES

              Type and Amount of
               Facility:            An aggregate principal amount of up to $250
                                    million will be available to Asarco
                                    subsequent to consummation of the Tender
                                    Offer under a senior secured revolving
                                    credit facility (the "R/C FACILITIES"). Such
                                    aggregate principal amount may, based on the
                                    actual amount of eligible accounts
                                    receivable of Asarco available to secure the
                                    R/C Facilities and in the sole discretion of
                                    the Arranger, be increased provided that the
                                    A Tender Loans are prepaid in an amount
                                    equal to the amount of such increase. Such
                                    aggregate principal amount may, based on the
                                    aggregate principal amount of Existing R/C
                                    Facilities (as defined below) available to
                                    Asarco and remaining in place subsequent to
                                    the consummation of the Tender Offer, be
                                    reduced in an amount equal to the amount of
                                    such Existing R/C Facilities.

              Availability:         The Loans under the R/C Facilities (the "R/C
                                    LOANS" and together with the A Tender Loans,
                                    the "LOANS") shall be available for
                                    borrowing, repayment and reborrowing during
                                    the period from the Tender Closing Date to
                                    the date thirty-three (33) months
                                    thereafter.

              Termination:          The R/C Facilities shall terminate, and all
                                    outstanding R/C Loans shall be repayable in

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       4


                                    full, on the date three (3) years after the
                                    Tender Closing Date.

              Purpose:              The proceeds of the R/C Loans shall be used
                                    (i) to refinance outstanding indebtedness of
                                    Asarco under the Existing R/C Facilities (as
                                    defined below) and in the event of an
                                    increase in the amount of the R/C Facilities
                                    above $250 million to repay a portion of
                                    outstanding A Tender Loans and (ii) for
                                    working capital purposes of Asarco. The
                                    "EXISTING R/C Facilities" means the credit
                                    facilities identified as such by Grupo
                                    Mexico and the Administrative Agent and
                                    which are on terms reasonably acceptable to
                                    the Arranger and Grupo Mexico. The aggregate
                                    principal amount of the Existing R/C
                                    Facilities is believed to total $800 million
                                    and to be for working capital purposes
                                    (based on publicly available information).

III.     CERTAIN PAYMENT PROVISIONS

         Fees and Interest Rates:   As set forth on Annex I.

         Optional Prepayments
         and Commitment Reductions: All or a portion of the Loans may be prepaid
                                    at any time and the unutilized portion of
                                    the Facilities may be terminated in whole or
                                    in part (in minimum amounts to be agreed
                                    upon) at the respective Borrower's option
                                    (except, in the case of the R/C Facilities
                                    prior to the Tender Closing Date, at the
                                    option of Grupo Mexico). A Tender Loans once
                                    prepaid may not be reborrowed.

         Mandatory Prepayments and
         Commitment Reductions:     The A Tender Loans will be prepaid, undrawn
                                    commitments for A Tender Loans will be
                                    reduced and replaced, and R/C Loans will be
                                    prepaid, in that order, to the extent of the
                                    net cash proceeds received from the
                                    following (in each case subject to customary
                                    exclusions to be agreed):

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       5


                                    -- any asset sales by Asarco and designated
                                       subsidiaries

                                    -- any debt issuances by Asarco (other than
                                       R/C Loans, except for R/C Loans required
                                       to reduce the A Tender Facility)

                                    -- any equity issuances by Asmex or Asarco
                                       (to any party other than Asmex or Grupo
                                       Mexico)

                                    -- any sale of Asarco stock

                                    -- any proceeds received by Asarco as a
                                       result of the exercise (by holders) of
                                       warrants relating to shares of Grupo
                                       Mexico held in a trust for the benefit
                                       of Asarco

IV.      GUARANTEES AND COLLATERAL

         Guarantees:                (a) All obligations of Asmex (and, after the
                                    Merger, of Asarco) in respect of the A
                                    Tender Facility will be unconditionally
                                    guaranteed by Grupo Mexico.

                                    (b) All obligations of Asarco in respect of
                                    the R/C Facilities will be unconditionally
                                    guaranteed by Grupo Mexico until the A
                                    Tender Loans are repaid in full (except as
                                    otherwise noted below in the case of
                                    Alternative R/C Facilities, and provided the
                                    conditions for release of the collateral for
                                    such guarantee obligations have been met),
                                    and by Asmex until consummation of the
                                    Merger.

                                    The Borrowers and guarantors are
                                    collectively referred to herein as "CREDIT
                                    PARTIES."

         Collateral:                (a) The obligations of Asmex in respect of
                                    the Facilities will be secured by a
                                    perfected first priority security interest
                                    in the Shares at any time owned by it.

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       6


                                    (b) The obligations of Grupo Mexico under
                                    its guarantees of the A Tender Facility and
                                    the R/C Facilities will be secured by a
                                    perfected first priority security interest
                                    in (1) shares of GMM representing 100% of
                                    the outstanding shares of GMM (other than
                                    shares not exceeding 1.50% held by others)
                                    and (2) all shares of Asarco held by Grupo
                                    Mexico, both immediately prior to the making
                                    of the A Tender Loans (presently
                                    representing approximately 9.8% of the
                                    outstanding shares of Asarco) and after the
                                    Merger. In addition, Grupo Mexico will
                                    covenant to maintain at all times, in
                                    support of its guarantees (so long as they
                                    remain in effect), an amount of unencumbered
                                    cash and short-term authorized money market
                                    investments (to be agreed with the Arranger,
                                    including deposits with approved banks,
                                    which in Mexico shall include only Banamex
                                    and Bancomer) equal to the lower of (A) 6
                                    months of interest on the outstanding A
                                    Tender Loans and (B) $100 million.

                                    (c) The obligations of Asarco in respect of
                                    the R/C Facilities will be secured by
                                    accounts receivable of Asarco (except as
                                    otherwise provided below in the case of
                                    "Alternative R/C Facilities").

                                    The security documentation will provide that
                                    in the event of default and enforcement or
                                    foreclosure at a time when both Asarco
                                    shares and GMM shares are held as collateral
                                    for the defaulted obligation, the collateral
                                    agent will be instructed to exercise
                                    reasonable efforts (for a period of up to 45
                                    days) to sell collateral consisting of
                                    Asarco shares before selling collateral
                                    consisting of GMM shares.

         Certain Releases of
          Collateral:               So long as no Default has occurred and is
                                    continuing:

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       7


                                    (a) The pledge of Asarco Shares securing
                                    guarantees of the R/C Loans will terminate
                                    when the A Tender Loans are repaid in full,
                                    PROVIDED that at such time (i) the R/C Loans
                                    and R/C Facilities are not Alternative R/C
                                    Loans and Alternative R/C Facilities, and
                                    (ii) Asarco is in compliance with its
                                    financial covenant relating to minimum
                                    EBITDA;

                                    (b) The pledge of Asarco Shares securing
                                    guarantees of the Alternative R/C Loans will
                                    terminate when (i) the A Tender Loans are
                                    repaid in full, and (ii) Asarco's senior
                                    unsecured long-term indebtedness is rated at
                                    or above BBB-by S&P and Baa3 by Moody's;

                                    (c) The pledge of GMM shares securing Grupo
                                    Mexico guarantees of the Facilities will be
                                    reduced pro rata (on a percentage basis)
                                    with reductions (by repayment) of the
                                    outstanding principal of the A Tender Loans,
                                    PROVIDED that (except as described in clause
                                    (d) below) the percentage of outstanding GMM
                                    shares remaining in pledge as security for
                                    guarantees of the Facilities may not thereby
                                    be reduced below 51% (or such higher
                                    percentage, if any, as is required for
                                    approval of corporate actions of GMM that
                                    are subject to shareholder consent and for
                                    election of a majority of the Board of
                                    Directors of GMM);

                                    (d) At such time as the outstanding
                                    principal of the A Tender Loans has been
                                    reduced (by repayment) to an amount equal to
                                    or less than 25% of the original principal
                                    amount of the A Tender Loans, all GMM shares
                                    remaining in pledge as security for
                                    guarantees of the Facilities will be
                                    released, PROVIDED that Asarco's senior
                                    unsecured long-term indebtedness is rated at
                                    or above BBB- by S&P and Baa3 by Moody's.

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       8


V.       CERTAIN CONDITIONS         The availability of the Facilities shall be
                                    conditioned upon satisfaction of, among
                                    other things, the following conditions
                                    precedent (the date upon which all such
                                    conditions precedent shall be satisfied and
                                    the A Tender Facility is first utilized
                                    being herein called the "TENDER CLOSING
                                    DATE") and the occurrence of the first
                                    utilization of the A Tender Facility on or
                                    before the date nine (9) months after
                                    September 24, 1999, and other conditions
                                    precedent customary for facilities and
                                    transactions of this type, including
                                    evidence of authority and receipt of
                                    necessary consents and approvals:

                                    (a) Each Credit Party shall have executed
                                    and delivered satisfactory definitive
                                    financing documentation with respect to the
                                    Facilities (the "CREDIT DOCUMENTATION").

                                    (b) On or prior to the Tender Closing Date,
                                    cash in an amount not less than $270 million
                                    shall be contributed to the equity capital
                                    of Asmex through Grupo Mexico (i) from
                                    existing cash resources of GMM in an
                                    aggregate amount not less than $250 million,
                                    and (ii) from existing cash resources of
                                    Grupo Mexico, in an amount not less than $20
                                    million.

                                    (c) Satisfaction of the Arranger with all
                                    material terms and conditions of the Tender
                                    Offer and the definitive Merger agreement.
                                    In addition, the Tender Offer and the Merger
                                    shall have been, or shall be concurrently,
                                    consummated in a manner satisfactory to the
                                    Administrative Agent (including satisfaction
                                    of the Administrative Agent with all
                                    determinations as to the satisfaction of
                                    material conditions thereunder) and no such
                                    condition of the Tender Offer or the
                                    definitive Merger agreement shall have been
                                    waived, amended, supplemented or otherwise
                                    modified without the prior written consent
                                    of the Administrative Agent; and

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       9


                                    Asmex shall have acquired shares of common
                                    stock of Asarco representing not less than
                                    80% of the ordinary voting power of all of
                                    the shares of capital stock of Asarco on a
                                    fully diluted basis, including stock of
                                    Asarco owned by Grupo Mexico and
                                    subsidiaries prior to the Tender Offer
                                    (determined in a manner satisfactory to the
                                    Arranger).

                                    (d) Grupo Mexico and Asarco shall have
                                    entered into a definitive merger agreement
                                    in form and substance satisfactory to the
                                    Administrative Agent, or Grupo Mexico shall
                                    have made satisfactory arrangements for the
                                    initiation of a statutory short-form merger,
                                    in each case pursuant to which Asarco will
                                    become a wholly-owned subsidiary of Grupo
                                    Mexico with Grupo Mexico able to exercise
                                    full control over the business and affairs
                                    of Asarco.

                                    (e) Invalidation or satisfaction of the
                                    requirements of Article 7 of Asarco's
                                    Restated Certificate of Incorporation with
                                    respect to the Transactions such that,
                                    following consummation of the Tender Offer,
                                    the Merger can be consummated without the
                                    affirmative vote of the holders of any
                                    Asarco shares other than Asmex; and
                                    invalidity, inapplicability or satisfaction
                                    (if necessary) of Article 10 of Asarco's
                                    Restated Certificate of Incorporation with
                                    respect to the Transactions or the
                                    Facilities.

                                    (f) Satisfaction or inapplicability of the
                                    requirements of Section 14A:10A of the New
                                    Jersey Business Corporation Act with respect
                                    to the Merger such that following
                                    consummation of the Tender Offer the Merger
                                    can be consummated without the affirmative
                                    vote of the holders of any Asarco shares
                                    other than Asmex.

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       10


                                    (g) Invalidation, redemption or other
                                    inapplicability of the rights issued under
                                    Asarco's Shareholder Rights Agreement dated
                                    as of January 28, 1998, as amended.

                                    (h) There not being any statute, rule,
                                    regulation, judgment, order or injunction
                                    promulgated, entered, enforced, enacted,
                                    issued or applicable to the Tender Offer or
                                    the Merger by any domestic or foreign
                                    federal or state governmental regulatory or
                                    administrative agency or authority or court
                                    or legislative body or commission which (i)
                                    prohibits, or imposes any material
                                    limitations on, Grupo Mexico's or Asmex'
                                    ownership or operation of all or a material
                                    portion of Asarco's businesses or assets,
                                    (ii) prohibits, or makes illegal the
                                    acceptance for payment, payment for or
                                    purchase of Asarco common stock or the
                                    consummation of the Tender Offer or the
                                    Merger, (iii) results in a material delay in
                                    or restricts the ability of the Grupo
                                    Mexico, or renders Grupo Mexico unable, to
                                    accept for payment, pay for or purchase some
                                    or all of the tendered shares of Asarco
                                    common stock, or (iv) imposes material
                                    limitations on the ability of Asmex or Grupo
                                    Mexico effectively to exercise full rights
                                    of ownership of the Asarco common stock,
                                    including, without limitation, the right to
                                    vote the Asarco common stock purchased by it
                                    on all matters properly presented to
                                    Asarco's shareholders.

                                    (i) The Lenders, the Administrative Agent
                                    and the Arranger shall have received all
                                    fees required to be paid, and all expenses
                                    for which invoices have been presented, on
                                    or before the Tender Closing Date.

                                    (j) The documents and materials filed
                                    publicly by Grupo Mexico (and its
                                    affiliates) and Asmex in connection with the
                                    Tender Offer shall have been furnished to
                                    the Administrative Agent and such documents

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       11


                                    and materials shall be reasonably
                                    satisfactory in form and substance to the
                                    Administrative Agent.

                                    (k) All regulatory and third party approvals
                                    and consents (including Hart-Scott-Rodino
                                    and other approvals and consents, if any)
                                    necessary in connection with the
                                    Transactions and the financing contemplated
                                    by the Amended and Restated Commitment
                                    Letter shall have been obtained and be in
                                    full force and effect and all applicable
                                    waiting periods shall have expired without
                                    any action being taken or threatened by any
                                    competent authority which could restrain,
                                    prevent or otherwise impose materially
                                    adverse conditions on the Transactions or
                                    the financing thereof, in each case on terms
                                    satisfactory to the Administrative Agent.

                                    (l) The Lenders shall have received (i)
                                    audited consolidated financial statements of
                                    Grupo Mexico, GMM and Grupo Ferroviario
                                    Mexicano, S.A. de C.V. ("RR") for the two
                                    most recent fiscal years (in the case of RR,
                                    one year) ended prior to the Tender Closing
                                    Date and (ii) unaudited interim consolidated
                                    financial statements of Grupo Mexico and of
                                    GMM for each quarterly period ended
                                    subsequent to the date of the latest
                                    financial statements delivered pursuant to
                                    clause (i) of this paragraph (l) as to which
                                    such financial statements are available.

                                    (m) The requisite Lenders shall be satisfied
                                    that upon making the initial A Tender Loans
                                    the requirements of Regulation U of the
                                    Board of Governors of the Federal Reserve
                                    System shall have been complied with.

                                    (n) The Lenders shall have received such
                                    legal opinions (including opinions (i) from
                                    counsel to Grupo Mexico and its subsidiaries
                                    and (ii) from such special and

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       12


                                    local counsel as may be required by the
                                    Administrative Agent), documents and other
                                    instruments as are customary for
                                    transactions of this type or as they may
                                    reasonably request.

                                    (o) The negotiation, execution and delivery
                                    of definitive Credit Documentation with
                                    respect to the R/C Facilities satisfactory
                                    to all parties. Such Credit Documentation
                                    will contain a borrowing base condition to
                                    each utilization of the R/C Facilities,
                                    requiring that borrowings thereunder not
                                    exceed 85% of the amount of eligible
                                    receivables of Asarco securing the R/C
                                    Loans; provided that if such requirement
                                    renders the R/C Facilities initially
                                    unutilizable by Asarco in an amount
                                    sufficient to satisfy the financing needs of
                                    Asarco on the Tender Closing Date, such
                                    Credit Documentation will provide (until
                                    such time as such borrowing base and
                                    security requirement can be satisfied) for
                                    an alternative mechanism (referred to herein
                                    as the "ALTERNATIVE R/C FACILITIES") for
                                    utilization by Asarco of the R/C Facilities,
                                    with the following principal features
                                    (borrowings under such alternative mechanism
                                    being herein referred to as the "ALTERNATIVE
                                    R/C LOANS"):

                                    -- Alternative R/C Loans will not be secured
                                       by Asarco assets

                                    -- Alternative R/C Loans will be (i)
                                       guaranteed by Asmex (until the Merger),
                                       with such guarantee secured by the
                                       Shares, and (ii) guaranteed by Grupo
                                       Mexico, with such guarantee secured by
                                       pledges of any Shares held by Grupo
                                       Mexico and of the shares of GMM; and such
                                       guarantee and pledges will not terminate
                                       or be fully released (notwithstanding
                                       contrary provisions elsewhere in this
                                       Term Sheet) until

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       13


                                       (in addition to other conditions noted
                                       above) Asarco's senior unsecured
                                       long-term indebtedness is rated at or
                                       above BBB- by S&P and Baa3 by Moody's.

                                    In the event that the working capital
                                    requirements of Asarco may be satisfied with
                                    Existing R/C Facilities subsequent to the
                                    consummation of the Tender Offer, the
                                    aggregate principal amount of the R/C
                                    Facilities may be reduced by the amount of
                                    such Existing R/C Facilities.

                                    (p) Hedging arrangements satisfactory to the
                                    Administrative Agent shall have been entered
                                    into (with counterparties acceptable to the
                                    Administrative Agent) for a "costless"
                                    collar covering production of GMM (with a
                                    minimum copper price of $0.75/lb with
                                    respect to 70,000 tons per annum) and, upon
                                    the consummation of the Tender Offer,
                                    covering production of Asarco (with a
                                    minimum copper price of $0.75/lb with
                                    respect to 100,000 tons per annum), in each
                                    case for a period of at least one year from
                                    the Tender Closing Date.

         On-Going Conditions:       The making of each extension of credit shall
                                    be conditioned on (a) the accuracy of all
                                    representations and warranties in the Credit
                                    Documentation (including, without
                                    limitation, the material adverse change and
                                    litigation representations) and (b) there
                                    being no default or event of default in
                                    existence at the time of, or after giving
                                    effect to the making of, such extension of
                                    credit.

                                    As used herein and in the Credit
                                    Documentation a "MATERIAL ADVERSE CHANGE"
                                    shall mean (i) prior to the consummation of
                                    the Merger, any event, development or
                                    circumstance that has had or could
                                    reasonably be expected to have a material

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       14


                                    adverse effect on (a) the Transactions, (b)
                                    the business, assets, property or condition
                                    (financial or otherwise) of Grupo Mexico and
                                    its subsidiaries, GMM and its subsidiaries,
                                    or Asarco and its subsidiaries, in each case
                                    taken as a whole (including any material
                                    change, prior to consummation of the Tender
                                    Offer, in capital structure or indebtedness
                                    of Asarco and any material acquisition or
                                    divestiture of assets of Asarco or any of
                                    its subsidiaries taken as a whole, that in
                                    any such case has had or could reasonably be
                                    expected to have such a material adverse
                                    effect); PROVIDED, HOWEVER, that any adverse
                                    effect that copper prices have had or may
                                    have on the business, operations, property
                                    or financial condition of Grupo Mexico and
                                    its subsidiaries, GMM and its subsidiaries,
                                    or Asarco and its subsidiaries, in each case
                                    taken as a whole, shall not be deemed to
                                    have such a material adverse effect for
                                    purposes of this clause (i)(b), or (c) the
                                    validity or enforceability of any of the
                                    Credit Documentation or the rights and
                                    remedies of the Administrative Agent and the
                                    Lenders thereunder; and (ii) after the
                                    consummation of the Merger, any event,
                                    development or circumstance that has had or
                                    could reasonably be expected to have a
                                    material adverse effect on (a) the
                                    Transactions, (b) the business, assets,
                                    property, condition (financial or otherwise)
                                    or prospects of Grupo Mexico and its
                                    subsidiaries, GMM and its subsidiaries, or
                                    Asarco and its subsidiaries, in each case
                                    taken as a whole, or (c) the validity or
                                    enforceability of any of the Credit
                                    Documentation or the rights and remedies of
                                    the Administrative Agent and the Lenders
                                    thereunder.

VI.      CERTAIN DOCUMENTATION
          MATTERS                   The Credit Documentation for the A Tender
                                    Facility and the R/C Facilities shall
                                    contain representations, warranties,
                                    covenants and events of default customary
                                    for financings of

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       15


                                    these types and other terms deemed
                                    appropriate by the Lenders, including,
                                    without limitation (but subject in
                                    appropriate cases to customary and other
                                    exceptions to be agreed), those specified
                                    below.

         Representations and
          Warranties:               Financial statements (including pro forma
                                    financial statements); absence of
                                    undisclosed liabilities; no material adverse
                                    change; corporate existence; compliance with
                                    law; corporate power and authority;
                                    enforceability of Credit Documentation; no
                                    conflict with law or contractual
                                    obligations; no material litigation; no
                                    default; ownership of property; liens;
                                    intellectual property; no burdensome
                                    restrictions; taxes; margin stock
                                    regulations; Federal Reserve regulations;
                                    ERISA; Investment Company Act; subsidiaries;
                                    environmental matters; solvency; labor
                                    matters; accuracy of disclosure; and
                                    creation and perfection of security
                                    interests.

         Affirmative Covenants:     Delivery of financial statements, reports,
                                    accountants' letters, annual projections,
                                    officers' certificates and other information
                                    requested by the Lenders; payment of certain
                                    other obligations; all payments under the
                                    Facilities to be made free and clear of and
                                    without reduction by reason of present or
                                    future taxes (customary gross-up, indemnity
                                    and evidence of payment provisions);
                                    continuation of business and maintenance of
                                    existence and material rights and
                                    privileges; compliance with laws and
                                    material contractual obligations;
                                    maintenance of property and insurance;
                                    maintenance of books and records; right of
                                    the Lenders to inspect property and books
                                    and records; notices of defaults, litigation
                                    and other material events; maintenance of
                                    required hedging arrangements; compliance
                                    with environmental laws; further assurances
                                    (including, without limitation, with respect
                                    to security interests in after-acquired

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       16


                                    property); ownership of GMM, of RR, of Asmex
                                    and, after the Merger, of Asarco; in the
                                    event of Asarco's utilization of the
                                    Alternative R/C Facility, Grupo Mexico to
                                    use its best efforts to cause Asarco to
                                    replace such utilization with R/C Loans that
                                    are not Alternative R/C Loans; and Grupo
                                    Mexico to use its best efforts to consummate
                                    the Merger as soon as practicable; and GMM
                                    to take reasonable steps to maintain
                                    investment grade ratings from S&P, Moody's
                                    and Duff & Phelps.




























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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       17


         Financial Covenants:       Financial covenants relating to



                                    (a) Grupo Mexico (consolidated with all
                                    subsidiaries, and consolidated with all
                                    subsidiaries other than Southern Peru Copper
                                    Corporation)

                                                (i) Maximum Debt to EBITDA ratio

                                                (ii) Minimum ratio of EBITDA to
                                                interest expense

                                                (iii) Maximum Debt to Capital
                                                ratio

                                    (b) GMM and subsidiaries (for so long as any
                                    Grupo Mexico guarantee is in effect)

                                                (i) Debt to Capital ratio not
                                                exceeding 45%

                                                (ii) Minimum Tangible Net Worth

                                                (iii) Minimum Collections to
                                                Debt Service ratio

                                                (iv) Minimum annual level of
                                                export receivables

                                                (v) Minimum ratio of export
                                                receivables to SEN debt service

                                                (vi) Minimum ratio of EBITDA to
                                                interest expense

                                    (c) Asarco

                                                Minimum EBITDA levels

         Negative Covenants:        Limitations on: indebtedness (including
                                    preferred stock of subsidiaries); voluntary
                                    prepayments of indebtedness other than under
                                    the Facilities; liens (including negative
                                    pledge on stock of GMM, Asarco and RR);
                                    guarantee obligations; mergers,
                                    consolidations, liquidations and
                                    dissolutions; sales of assets; leases;
                                    capital expenditures; investments, loans and
                                    advances; dividends

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       18


                                    and other payments in respect of capital
                                    stock; transactions with affiliates; sale
                                    and leasebacks; changes in fiscal year; and
                                    changes in lines of business.

         Special Covenant of Asmex: Asmex shall covenant that it will not engage
                                    in any activity other than the Transactions,
                                    the A Tender Facility and activities
                                    necessary to effect the same.

         Events of Default:         (a) A Borrower shall fail to make any
                                    payment of principal of any Loan when due.

                                    (b) A Borrower shall fail to make any
                                    payment of interest or fees on any Loan, or
                                    any other payments required under the Credit
                                    Documentation, within 3 business days of due
                                    date.

                                    (c) Any representation or warranty by a
                                    Credit Party contained in the Credit
                                    Documentation or any certificate required to
                                    be delivered thereunder shall prove to have
                                    been incorrect in a material respect when
                                    made or deemed made.

                                    (d) A Credit Party (or any of its
                                    subsidiaries) shall fail to perform or
                                    observe any of its financial or other
                                    covenants under the Credit Documentation
                                    (subject to grace periods to be agreed).

                                    (e) Customary bankruptcy events of default,
                                    including (i) Grupo Mexico, GMM, Asarco or
                                    any of their subsidiaries (except for
                                    non-material subsidiaries (to be defined))
                                    shall consent to the appointment of a
                                    receiver for itself or a substantial part of
                                    its property, (ii) Grupo Mexico, GMM, Asarco
                                    or any of their subsidiaries (except for
                                    non-material subsidiaries) shall seek relief
                                    under any applicable bankruptcy law or (iii)
                                    an involuntary bankruptcy or like proceeding
                                    shall have been commenced against Grupo
                                    Mexico, GMM, Asarco or any of their
                                    subsidiaries (except for non-material

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       19


                                    subsidiaries) and such proceeding shall not
                                    have been stayed or vacated for a period of
                                    60 days after the date it was commenced.

                                    (f) The security interest in any collateral
                                    furnished by a Credit Party listed above
                                    under "Guarantees and Collateral" shall
                                    cease to be a first priority perfected
                                    security interest as required hereunder.

                                    (g) Failure by a Credit Party to pay when
                                    due (after taking into account applicable
                                    grace periods) any unsecured or secured
                                    indebtedness (including capitalized lease
                                    obligations) or any default that permits the
                                    acceleration of the maturity of any such
                                    indebtedness and obligations or termination
                                    of any capital lease, aggregating in the
                                    case of all such indebtedness and
                                    obligations an amount equal to or exceeding
                                    threshold amounts to be agreed.

                                    (h) A final judgment or judgments for the
                                    payment of money shall be entered against
                                    Grupo Mexico, GMM, Asarco or any of their
                                    subsidiaries (except for non-material
                                    subsidiaries, and except, in the case of
                                    Asarco and its subsidiaries prior to
                                    consummation of the Tender Offer, judgments
                                    the existence of which was already disclosed
                                    and publicly available (or otherwise known
                                    by officers of the Arranger or Chase working
                                    on the Transactions) prior to September 24,
                                    1999) in an aggregate amount for all such
                                    persons equal to or exceeding threshold
                                    amounts to be agreed and which have not been
                                    bonded, stayed or satisfied for a period of
                                    30 days or more.

                                    (i) There shall occur one or more ERISA
                                    Events which individually or in the
                                    aggregate results in or could reasonably be
                                    expected to result in a material adverse
                                    change; or there shall exist an amount of
                                    unfunded benefit liabilities (as defined in
                                    the

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       20


                                    Statement of Financial Accounting Standards
                                    No. 87), individually or in the aggregate
                                    for all Plans (excluding for purposes of
                                    such computation any Plans with respect to
                                    which assets exceed benefit liabilities),
                                    which could reasonably be expected to result
                                    in a material adverse change.

                                    (j) There shall occur a change in control of
                                    GMM, Asmex or (after the consummation of the
                                    Tender Offer) Asarco; or Persons (to be
                                    identified) controlling Grupo Mexico (I.E.,
                                    having the power to elect a majority of the
                                    members of the Board of Directors of Grupo
                                    Mexico) on September 24, 1999, shall cease
                                    to maintain such control.

                                    (k) Default in the performance or
                                    observation of any term or condition in any
                                    material contract of Grupo Mexico, GMM or
                                    Asarco, or any of their subsidiaries, in
                                    each case taken as a whole, that could
                                    reasonably be expected to result in a
                                    material adverse change.

                                    (l) So long as any obligations under the A
                                    Tender Facility remain outstanding, any
                                    Default or acceleration under the A Tender
                                    Facility, or the R/C Facilities (including
                                    Alternative R/C Facilities) or the secured
                                    export note or other long-term debt
                                    obligations of GMM (with a threshhold
                                    amount, in the case of GMM, of $30 million).

         Voting:                    Amendments and waivers with respect to the
                                    Credit Documentation shall require the
                                    approval of Lenders holding not less than a
                                    majority of the aggregate amount of the
                                    Loans thereunder and commitments under the
                                    related Facilities, except that (a) the
                                    consent of each Lender directly affected
                                    thereby shall be required with respect to
                                    (i) changes in the maturity of any Loan,

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       21


                                    (ii) reductions in the rate of interest or
                                    any fee or extensions of any due date
                                    thereof, (iii) increases in the amount or
                                    extensions of the expiry date of any
                                    Lender's commitment and (iv) modifications
                                    to the pro rata provisions of the Credit
                                    Documentation and (b) the consent of 100% of
                                    the Lenders shall be required with respect
                                    to (i) modifications to any of the voting
                                    percentages and (ii) releases of any
                                    guarantee other than of a non-material
                                    subsidiary (to be defined) or all or any
                                    substantial part of the collateral.

         Assignments and
          Participations:           The Lenders shall be permitted to assign and
                                    sell participations in their Loans and
                                    commitments, subject, in the case of
                                    assignments (other than to another Lender or
                                    to an affiliate of a Lender), to the consent
                                    of the Administrative Agent and Grupo Mexico
                                    (which consent in each case shall not be
                                    unreasonably withheld, provided that if a
                                    default shall have occurred and be
                                    continuing Grupo Mexico's consent shall not
                                    be necessary). In the case of partial
                                    assignments (other than to another Lender or
                                    to an affiliate of a Lender of any interest
                                    in the A Tender Facility), the minimum
                                    assignment amount shall be $5,000,000 unless
                                    otherwise agreed by Grupo Mexico and the
                                    Administrative Agent. Each assignment shall
                                    be subject to payment to the Administrative
                                    Agent of a processing fee of $3,500.
                                    Participants shall have the same benefits as
                                    the Lenders from which they acquired their
                                    participations with respect to yield
                                    protection and increased cost provisions.
                                    Voting rights of participants shall be
                                    limited to those matters with respect to
                                    which the affirmative vote of the Lender
                                    from which it purchased its participation
                                    would be required as described in items (a)
                                    and (b) of the paragraph on "Voting" above.
                                    Pledges of Loans in accordance with
                                    applicable law shall be permitted without
                                    restriction.

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       22


         Yield Protection:          The Credit Documentation shall contain
                                    customary provisions (a) protecting the
                                    Lenders against increased costs or loss of
                                    yield resulting from changes in reserve,
                                    tax, capital adequacy and other requirements
                                    of law and from the imposition of or changes
                                    in withholding or other taxes and (b)
                                    indemnifying the Lenders for "breakage
                                    costs" incurred in connection with, among
                                    other things, any prepayment of a Eurodollar
                                    Loan (as defined in Annex I) on a day other
                                    than the last day of an interest period with
                                    respect thereto.

         Expenses and
           Indemnification:         The Borrowers shall pay (a) all reasonable
                                    out-of-pocket expenses of the Administrative
                                    Agent and the Arranger associated with the
                                    syndication of the Credit Facilities and the
                                    preparation, execution, delivery and
                                    administration of the Credit Documentation
                                    and any amendment or waiver with respect
                                    thereto (including the reasonable fees,
                                    disbursements and other charges of counsel)
                                    and (b) all out-of-pocket expenses of the
                                    Administrative Agent and (after an Event of
                                    Default) of the Lenders (including the fees,
                                    disbursements and other charges of counsel)
                                    in connection with the enforcement of the
                                    Credit Documentation.

                                    The Administrative Agent, the Arranger and
                                    the Lenders (and their affiliates and their
                                    respective officers, directors, employees,
                                    advisors and agents) will have no liability
                                    for, and will be indemnified and held
                                    harmless against, any loss, liability, cost
                                    or expense incurred in respect of the
                                    financing contemplated hereby or the use or
                                    the proposed use of proceeds thereof (except
                                    to the extent resulting from the gross
                                    negligence or willful misconduct of the
                                    indemnified party).

         Governing Law and Forum:   State of New York.

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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.
<PAGE>
                                       23


         Counsel to the
         Administrative Agent
         and the Arranger:          Milbank, Tweed, Hadley & McCloy LLP, and
                                    Ritch, Heather y Mueller S.C.



























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[GRAPHIC OMITTED]                                     Grupo Mexico, S.A. de C.V.


<PAGE>
                                                               Exhibit 99(b)(3)

[GRAPHIC OMITTED][GRAPHIC OMITTED]










THE CHASE MANHATTAN BANK                                  CHASE SECURITIES INC.
270 Park Avenue                                                 270 Park Avenue
New York, New York  10017                             New York, New York  10017



                                                                 October 7, 1999


                                ASMEX Corporation
                        Senior Secured Credit Facilities
                  Second Amended and Restated Commitment Letter

Grupo Mexico, S.A. de C.V.
Baja California 200
Colonia Roma Sur
Mexico, D.F.  Mexico
06760

Attention:  Daniel Tellechea

Ladies and Gentlemen:

                  This Second Amended and Restated Commitment Letter hereby,
subject to the terms and conditions set forth herein, amends and restates the
Amended and Restated Commitment Letter dated October 5, 1999 (the "AMENDED AND
RESTATED COMMITMENT"), among Grupo Mexico, Chase and CSI (each as defined
below). You have advised The Chase Manhattan Bank ("CHASE") and Chase Securities
Inc. ("CSI") that ASMEX Corporation, a Delaware corporation (the "BORROWER"), a
wholly-owned subsidiary of Grupo Mexico, S.A. de C.V., a Mexican corporation
("GRUPO MEXICO"), intends to make a cash tender offer (the "TENDER OFFER") for
common stock of Asarco Incorporated, a New Jersey corporation ("ASARCO"),
representing at least 80% of the ordinary voting power of all of the shares of
capital stock of Asarco on a fully diluted basis (including stock of Asarco
owned by Grupo Mexico and
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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.

<PAGE>
                                       2


subsidiaries prior to the Tender Offer), to be followed by the merger of the
Borrower into Asarco, with Asarco thereby becoming a wholly-owned subsidiary of
Grupo Mexico.

                  We understand that to provide funds for the Tender Offer and
to pay related fees and expenses, Grupo Mexico requires that senior secured
financing be made available to the Borrower in the amount of up to $823 million
(the "A TENDER FACILITY"). We further understand that, following the successful
completion of the Tender Offer, the Borrower is to be merged into Asarco with
Asarco thereby becoming a wholly-owned subsidiary of Grupo Mexico (the "MERGER"
and, together with the Tender Offer, the "TRANSACTIONS"), and that (whether or
not the Merger is immediately effected) Grupo Mexico will require senior
financing for Asarco (the "R/C FACILITIES") in an aggregate amount equal to $250
million in order to refinance certain indebtedness of Asarco and to provide
funds for ongoing general corporate purposes. The A Tender Facility and the R/C
Facilities are herein collectively referred to as the "FACILITIES".

                  In that connection, you have requested that CSI agree to
structure, arrange and syndicate the Facilities, and that Chase commit to
provide the entire principal amount of the Facilities and to serve as
administrative agent for the Facilities.

                  CSI is pleased to advise you that it is willing to act as
exclusive advisor, lead arranger and book manager for the Facilities.

                  Furthermore, Chase is pleased to advise you of its commitment
to provide the entire amount of the Facilities upon the terms and subject to the
conditions set forth or referred to in this second amended and restated
commitment letter (the "SECOND AMENDED AND RESTATED COMMITMENT LETTER"), in the
Second Amended and Restated Summary of Terms and Conditions attached hereto as
Exhibit A (the "TERM SHEET") and in the Fee Letter dated September 24, 1999 (the
"FEE LETTER"). We intend to syndicate the Facilities to a group of financial
institutions (together with Chase, the "LENDERS") identified by us in
consultation with you. Chase shall be relieved of its obligation to provide the
entire amount of the Facilities to the extent that the offers of Lenders other
than Chase to provide any portion of the Facilities are accepted.

                  CSI intends to commence syndication efforts promptly, and you
agree actively to assist CSI in its efforts to complete a syndication
satisfactory to it prior to the Tender Closing Date referred to in the Term
Sheet. Such assistance shall include (a) your using commercially reasonable
efforts to ensure that the syndication efforts benefit materially from your
existing lending relationships, (b) direct contact between senior management and
advisors of yourselves and the Borrower and the proposed Lenders, (c) assistance
in the preparation of a Confidential Information Memorandum and other marketing
materials to be used in connection with the syndication and (d) the hosting,
with CSI, of one or more meetings of prospective Lenders.

                  It is agreed that Chase will act as the sole and exclusive
Administrative Agent for the Facilities and as the Collateral Agent in
connection with the Facilities, and that CSI will act as the sole and exclusive
advisor, arranger and book manager for the Facilities, and each will, in such
capacities, perform the duties and exercise the authority customarily performed
and exercised by it in such roles. You agree that no other agents, co-agents,
arrangers or book managers will be appointed, no other titles will be awarded
and no compensation (other than that

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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.

<PAGE>
                                       3


expressly contemplated by the Term Sheet and the Fee Letter referred to below)
will be paid in connection with the Facilities unless you and we shall so agree.

                  CSI will (in consultation with you) manage all aspects of the
syndication, including decisions as to the selection of institutions to be
approached and when they will be approached, when their commitments will be
accepted, which institutions will participate, the allocations of the
commitments among the Lenders and the amount and distribution of fees among the
Lenders. To assist CSI in its syndication efforts, you agree promptly to prepare
and provide to CSI and Chase all information with respect to Grupo Mexico, Grupo
Minero Mexico, S.A. de C.V., a Mexican corporation ("GMM") , the Borrower and
their respective subsidiaries, the Transactions and the other matters
contemplated hereby, including all financial information and projections (the
"PROJECTIONS"), as we may reasonably request in connection with the arrangement
and syndication of the Facilities. You hereby represent and covenant that (a)
all information other than the Projections (the "INFORMATION") that has been or
will be made available to Chase or CSI by you or any of your representatives is
or will be, when furnished, complete and correct in all material respects and
does not or will not, when furnished, contain any untrue statement of a material
fact or omit to state a material fact necessary in order to make the statements
contained therein not materially misleading in light of the circumstances under
which such statements are made and (b) the Projections that have been or will be
made available to Chase or CSI by you or any of your representatives have been
or will be prepared in good faith based upon reasonable assumptions. You
understand that in arranging and syndicating the Facilities we may use and rely
on the Information and Projections without independent verification thereof.

                  As consideration for Chase's commitment hereunder and CSI's
agreement to perform the services described herein, you agree to pay and to
cause the Borrower to pay to Chase the non-refundable fees set forth in Annex I
to the Term Sheet and in the Fee Letter.

                  Chase's commitment hereunder and CSI's agreement to perform
the services described herein are subject to

                  (a) (i) there not occurring or becoming known to us any
         material adverse condition or material adverse change in or affecting
         the business, operations, property or financial condition of Grupo
         Mexico and its subsidiaries, GMM and its subsidiaries, or Asarco and
         its subsidiaries, in each case taken as a whole, which (in the case of
         Asarco and its subsidiaries) is not already disclosed and publicly
         available or otherwise known by any of our officers who is working with
         you on the Transactions; provided, HOWEVER, that any adverse effect
         that copper prices have had or may have on the business, operations,
         property or financial condition of Grupo Mexico and its subsidiaries,
         GMM and its subsidiaries, or Asarco and its subsidiaries, in each case
         taken as a whole, shall not be deemed to be such a material adverse
         condition or material adverse change for purposes of this clause
         (a)(i); and (ii) our not becoming aware after September 24, 1999, of
         any information or other matter affecting Grupo Mexico and its
         subsidiaries, GMM and its subsidiaries, Asarco and its subsidiaries, in
         each case taken as a whole, or the transactions contemplated hereby
         which is inconsistent in a material and adverse manner

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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.
<PAGE>
                                       4


         with any such information or other matter disclosed to us prior to
         September 24, 1999, and which (in the case of Asarco and its
         subsidiaries) is not already disclosed and publicly available or
         otherwise known by any of our officers who is working with you on the
         Transactions,

                  (b) there shall not have been any statute, rule, regulation,
         judgment, order or injunction promulgated, entered, enforced, enacted,
         issued or applicable to the Tender Offer or the Merger by any domestic
         or foreign federal or state governmental regulatory or administrative
         agency or authority or court or legislative body or commission which
         (i) prohibits, or imposes any material limitations on, Grupo Mexico's
         or Asmex' ownership or operation of all or a material portion of
         Asarco's businesses or assets, (ii) prohibits, or makes illegal the
         acceptance for payment, payment for or purchase of Asarco common stock
         or the consummation of the Tender Offer or the Merger, (iii) results in
         a material delay in or restricts the ability of Grupo Mexico, or
         renders Grupo Mexico unable, to accept for payment, pay for or purchase
         some or all of the tendered shares of Asarco common stock, or (iv)
         imposes material limitations on the ability of Asmex or Grupo Mexico
         effectively to exercise full rights of ownership of the Asarco common
         stock, including, without limitation, the right to vote the Asarco
         common stock purchased by it on all matters properly presented to
         Asarco's shareholders,

                  (c) there not having occurred (i) after the date hereof to
         November 30, 1999, a general banking moratorium established by Federal
         or state authorities, a generally recognized capital markets crisis, as
         evidenced by a cumulative 20% decline in the Dow Jones Industrial
         Average over a period of five (5) consecutive trading days, or a
         virtual cessation in bank and other private debt financings or the
         introduction of additional material government restrictions imposed
         upon lending institutions which materially affect the type of
         transactions contemplated thereby, and (ii) after November 30, 1999, a
         material disruption of or material adverse change in U.S. or developed
         country financial, banking or capital market conditions that, in our
         judgment, is reasonably likely to materially impair the syndication of
         the Facilities,

                  (d) our satisfaction that prior to and during the syndication
         of the Facilities there shall be no competing offering, placement or
         arrangement of any debt securities or bank financing by or on behalf of
         Grupo Mexico or any affiliate thereof,

                  (e) in the case of the A Tender Facility, our satisfaction
         with the conditions of the Tender Offer which will include, in any
         event (unless otherwise satisfied in connection with the definitive
         Merger agreement with Asarco), (i) invalidation, redemption or other
         inapplicability of the rights issued under Asarco's Shareholder Rights
         Agreement dated as of January 28, 1998, as amended, (ii) invalidation
         or satisfaction of the requirements of Article 7 of Asarco's Restated
         Certificate of Incorporation with respect to the Transactions such that
         following consummation of the Tender Offer the Merger may be
         consummated without the affirmative vote of the holders of any Asarco
         shares other than the Borrower, (iii) invalidity, inapplicability or
         satisfaction (if necessary) of Article 10 of Asarco's Restated
         Certificate of Incorporation with respect to the Transactions or the
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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.
<PAGE>
                                       5


         Facilities, (iv) satisfaction or inapplicability of the requirements of
         Section 14A:10A of the New Jersey Business Corporation Act with respect
         to the Merger such that following consummation of the Tender Offer the
         Merger may be consummated without the affirmative vote of the holders
         of any Asarco shares other than the Borrower and (v) obtaining all
         regulatory approvals and consents (including Hart-Scott-Rodino and
         other approvals or consents, if any) necessary to effect the
         Transactions,

                  (f) in the case of the R/C Facilities, prior or concurrent
         disbursement of the A Tender Facility, successful consummation of the
         Tender Offer and our satisfaction with the terms and conditions of the
         definitive Merger agreement,

                  (g) the negotiation, execution and delivery on or prior to the
         Tender Closing Date of definitive documentation with respect to the
         Facilities satisfactory to all parties, and

                  (h) the other conditions set forth or referred to in the Term
         Sheet.

The terms and conditions of Chase's commitments hereunder and of the Facilities
are not limited to those set forth herein and in the Term Sheet and Fee Letter.
Those matters that are not covered by the provisions hereof and of the Term
Sheet are subject to the approval and agreement of Chase, CSI and Grupo Mexico.
Notwithstanding the foregoing, the Term Sheet and Fee Letter are intended to
reflect all material closing conditions, representations and warranties,
covenants and events of default, subject however, in each case, to such
additional provisions as shall be appropriate to take into account developments
after September 24, 1999.

                  You agree (a) to indemnify and hold harmless Chase, CSI, their
affiliates and their respective officers, directors, employees, advisors, and
agents (each, an "INDEMNIFIED PERSON") from and against any and all losses,
claims, damages and liabilities to which any such indemnified person may become
subject arising out of or in connection with this Second Amended and Restated
Commitment Letter, the Facilities, the use of the proceeds thereof, the
Transactions or any related transaction or any claim, litigation, investigation
or proceeding relating to any of the foregoing, regardless of whether any
indemnified person is a party thereto, and to reimburse each indemnified person
upon demand for any legal or other expenses incurred in connection with
investigating or defending any of the foregoing, PROVIDED that the foregoing
indemnity will not, as to any indemnified person, apply to losses, claims,
damages, liabilities or related expenses to the extent they are found by a
final, non-appealable judgment of a court to arise from the willful misconduct
or gross negligence of such indemnified person, and (b) to reimburse Chase, CSI
and their affiliates on demand for all reasonable and documented out-of-pocket
expenses (including due diligence expenses, syndication expenses, consultant's
fees and expenses, travel expenses, and reasonable fees, charges and
disbursements of counsel) incurred in connection with the Facilities and any
related documentation (including this Second Amended and Restated Commitment
Letter, the Term Sheet, the Fee Letter and the definitive financing
documentation) or (without duplication of fees or costs for administrative
services covered in the Fee Letter) the administration, amendment, modification
or waiver thereof. No indemnified person shall be liable for any damages arising
from the use by others of Information or other materials obtained through
electronic, telecommunications or other information transmission
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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.


<PAGE>
                                       6


systems, or for any special, indirect, consequential or punitive damages in
connection with the Facilities.

                  You acknowledge that Chase and/or CSI may be providing debt
financing, equity capital or other services (including financial advisory
services) to other companies in respect of which you may have conflicting
interests regarding the transactions described hereby and otherwise. Neither
Chase nor CSI will use confidential information obtained from you by virtue of
the transactions contemplated hereby or other relationships with you in
connection with the performance by Chase or CSI of services for other companies,
and neither Chase nor CSI will furnish any such information to other companies.
You also acknowledge that neither Chase nor CSI has any obligation to use in
connection with the transactions contemplated hereby, or to furnish to you,
confidential information obtained from other companies.

                  This Second Amended and Restated Commitment Letter shall not
be assignable by you without the prior written consent of Chase and CSI (and any
purported assignment without such consent shall be null and void), is intended
to be solely for the benefit of the parties hereto and is not intended to confer
any benefits upon, or create any rights in favor of, any person other than the
parties hereto. This Second Amended and Restated Commitment Letter may not be
amended or waived except by an instrument in writing signed by you, Chase and
CSI. This Second Amended and Restated Commitment Letter may be executed in any
number of counterparts, each of which shall be an original, and all of which,
when taken together, shall constitute one agreement. Delivery of an executed
signature page of this Second Amended and Restated Commitment Letter by
facsimile transmission shall be effective as delivery of a manually executed
counterpart hereof. This Second Amended and Restated Commitment Letter and the
Fee Letter set forth the entire understanding of the parties with respect
thereto. This Second Amended and Restated Commitment Letter shall be governed
by, and construed in accordance with, the laws of the State of New York.

                  This Second Amended and Restated Commitment Letter is
delivered to you on the understanding that neither this Second Amended and
Restated Commitment Letter, the Term Sheet or the Fee Letter nor any of their
terms or substance shall be disclosed, directly or indirectly, to any other
person except (a) to your officers, agents and advisors who are directly
involved in the consideration of this matter or (b) as may be compelled in a
judicial or administrative proceeding or as otherwise required by law (in which
case you agree to inform us promptly thereof), PROVIDED, that the foregoing
restrictions shall cease to apply (except in respect of the Fee Letter and its
terms and substance) after this Second Amended and Restated Commitment Letter
has been accepted by you.

                  The compensation, reimbursement, indemnification and
confidentiality provisions contained herein and in the Fee Letter shall remain
in full force and effect regardless of whether definitive financing
documentation shall be executed and delivered and notwithstanding the
termination of this Second Amended and Restated Commitment Letter or Chase's
commitments hereunder.

                  If the foregoing correctly sets forth our agreement, please
indicate your acceptance of the terms hereof and of the Term Sheet by returning
to us executed counterparts
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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.
<PAGE>
                                       7



hereof not later than 11:00 a.m., New York City time, on October 7, 1999 (at
which time this Second Amended and Restated Commitment Letter shall expire if
not executed and delivered by you). Further, this Second Amended and Restated
Commitment Letter and the amendments of the Amended and Restated Commitment and
the Summary of Terms and Conditions attached thereto as Exhibit A set forth
herein and in the Term Sheet shall not become effective UNLESS Grupo Mexico and
Asarco execute and deliver a definitive Merger agreement satisfactory to Chase
and CSI, not later than 5:00 p.m., New York City time, on October 15, 1999.
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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.


<PAGE>
                                       8


                  Chase and CSI are pleased to have been given the opportunity
to assist you in connection with this important financing.

                  Upon the effectiveness of this Second Amended and Restated
Commitment Letter, references in the Fee Letter to the "Commitment Letter"
(other than the reference thereto in clause (i) of the second paragraph of the
Fee Letter) shall mean the Amended and Restated Commitment, as amended and
restated hereby. Except as set forth in the preceding sentence, the Fee Letter
shall remain unmodified and in full force and effect.

                                 Very truly yours,

                                 THE CHASE MANHATTAN BANK



                                 By:  /s/ Robert Anastasio
                                      ------------------------------------
                                      Name:  Robert Anastasio
                                      Title: Vice President

                                 CHASE SECURITIES INC.



                                 By:  /s/ Anne S. Wallace
\                                     ------------------------------------
                                      Name:  Anne S. Wallace
                                      Title: Vice President



Accepted and agreed to as of the date first written above by:

GRUPO MEXICO, S.A. DE C.V.


By: /s/ Daniel Tellechea Salido
   ----------------------------------
   Name:  Daniel Tellechea Salido
   Title: Managing Director For
          Administration and Finance

By: /s/ Genaro Guerrero Diaz Mercado
   ------------------------------------
   Name:  Genaro Guerrero Diaz Mercado
   Title: Treasurer


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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.

<PAGE>



                                                                       Exhibit A



                        SENIOR SECURED CREDIT FACILITIES
           Second Amended and Restated Summary of Terms and Conditions

                                 October 7, 1999

                  AS USED HEREIN, CAPITALIZED TERMS NOT OTHERWISE DEFINED HEREIN
SHALL HAVE THE RESPECTIVE MEANINGS ASCRIBED TO THEM IN THE SECOND AMENDED AND
RESTATED COMMITMENT LETTER TO WHICH THIS SECOND AMENDED AND RESTATED SUMMARY OF
TERMS AND CONDITIONS IS ATTACHED.

                  This Second Amended and Restated Summary of Terms and
Conditions hereby, subject to the terms and conditions set forth in the Amended
and Restated Commitment Letter, amends and restates the Amended and Restated
Summary of Terms and Conditions dated October 5, 1999. The following sets forth
the terms and conditions for the senior secured credit facilities that will be
made available to ASMEX Corporation, a Delaware corporation ("ASMEX"), in
connection with Asmex' proposed cash tender offer (the "TENDER OFFER" and,
together with the Merger defined below, the "TRANSACTIONS") for shares of common
stock of Asarco Incorporated (the "Shares"), a New Jersey corporation
("ASARCO"), representing not less than 80% of the ordinary voting power of all
of the shares of capital stock of Asarco on a fully diluted basis, including
stock of Asarco owned by Grupo Mexico, S.A. de C.V., ("GRUPO MEXICO") and
subsidiaries prior to the Tender Offer (determined in a manner satisfactory to
the Arranger). The conditions precedent to the obligation of Asmex to purchase
the Shares pursuant to the Tender Offer will include, unless otherwise satisfied
in connection with the definitive Merger agreement with Asarco, the following:
(i) invalidation, redemption or other inapplicability of the rights issued under
Asarco's Shareholder Rights Agreement dated as of January 28, 1998, as amended,
(ii) invalidation or satisfaction of the requirements of Article 7 of Asarco's
Restated Certificate of Incorporation with respect to the Transactions such
that, following consummation of the Tender Offer, the Merger can be consummated
without the affirmative vote of the holders of any Asarco shares other than
Asmex, (iii) invalidity, inapplicability or satisfaction (if necessary) of
Article 10 of Asarco's Restated Certificate of Incorporation with respect to the
Transactions or the Facilities, (iv) satisfaction or inapplicability of the
requirements of Section 14A:10A of the New Jersey Business Corporation Act with
respect to the Merger such that following consummation of the Tender Offer the
Merger can be consummated without the affirmative vote of the holders of any
Asarco shares other than Asmex and (v) obtaining all regulatory approvals and
consents (including Hart-Scott-Rodino, and other approvals or consents, if any)
necessary to effect the Transactions. The purchase of shares will be funded
through credit facilities (the "A Tender Facility" referred to below) together
with certain cash from Grupo Minero Mexico, S.A. de C.V. ("GMM") and Grupo
Mexico. Following the purchase of the Shares pursuant to the Tender Offer,
Asmex, a direct wholly-owned subsidiary of Grupo Mexico, is to be merged into
Asarco with Asarco thereby becoming a wholly-owned subsidiary of Grupo Mexico
and with Asarco shareholders receiving solely cash consideration (the "MERGER").
The following also sets forth the terms and conditions for the other senior
credit facilities (the "R/C Facilities" referred to

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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.
<PAGE>
                                       2


below) that will be made available to Asarco upon and subsequent to consummation
of the Tender Offer.



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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.

<PAGE>
                                       3


I.       PARTIES

         Borrowers:                     Under the A Tender Facility, ASMEX
                                        Corporation ("ASMEX") and, after the
                                        Merger, Asarco; and under the R/C
                                        Facilities, Asarco (each of Asmex and
                                        Asarco being sometimes referred to below
                                        as a "BORROWER").

         Guarantor(s):                  Under the A Tender Facility, Grupo
                                        Mexico; and under the R/C Facilities,
                                        Grupo Mexico and, until consummation of
                                        the Merger, Asmex.

         Advisor, Lead Arranger
         and Book Manager:              Chase Securities Inc. (in such capacity,
                                        the "ARRANGER").

         Administrative Agent:          The Chase Manhattan Bank ("CHASE" and,
                                        in such capacity, the "ADMINISTRATIVE
                                        AGENT").

         Lenders:                       A syndicate of banks, financial
                                        institutions and other entities,
                                        including Chase, arranged by the
                                        Arranger in consultation with Grupo
                                        Mexico (collectively, the "LENDERS").

II.      TYPES AND AMOUNTS OF
         CREDIT FACILITIES

         1.       A TENDER FACILITY

                  Type and Amount of
                  Facility:             An aggregate principal amount of up to
                                        $823 million will be available to Asmex
                                        under a senior secured credit facility
                                        (the "A TENDER FACILITY").

                  Availability:         The Loans under the A Tender Facility
                                        (the "A TENDER LOANS") shall be made in
                                        a single drawing on the Tender Closing
                                        Date (as defined below); provided that
                                        in the event of tender of less than 100%
                                        of the Shares of Asarco (other than
                                        those owned by Grupo Mexico and
                                        subsidiaries) in the Tender Offer, the
                                        unused portion of the commitments under
                                        the A Tender Facility


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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.

<PAGE>
                                       4


                                        will be reserved for drawing on the
                                        Merger closing date for payment for the
                                        remaining Shares of Asarco.

                  Amortization:         The A Tender Loans shall be repayable in
                                        full on the date eighteen (18) months
                                        after the Tender Closing Date (the date
                                        on which the A Tender Loans are
                                        repayable, the "MATURITY DATE").

                  Purpose:              The proceeds of the A Tender Loans shall
                                        be used to purchase Shares.

         2.       R/C FACILITIES

                  Type and Amount of
                  Facility:             An aggregate principal amount of up to
                                        $250 million will be available to Asarco
                                        subsequent to consummation of the Tender
                                        Offer under a senior secured revolving
                                        credit facility (the "R/C FACILITIES").
                                        Such aggregate principal amount may,
                                        based on the actual amount of eligible
                                        accounts receivable of Asarco available
                                        to secure the R/C Facilities and in the
                                        sole discretion of the Arranger, be
                                        increased provided that the A Tender
                                        Loans are prepaid in an amount equal to
                                        the amount of such increase. Such
                                        aggregate principal amount may, based on
                                        the aggregate principal amount of
                                        Existing R/C Facilities (as defined
                                        below) available to Asarco and remaining
                                        in place subsequent to the consummation
                                        of the Tender Offer, be reduced in an
                                        amount equal to the amount of such
                                        Existing R/C Facilities.

                  Availability:         The Loans under the R/C Facilities (the
                                        "R/C LOANS" and together with the A
                                        Tender Loans, the "LOANS") shall be
                                        available for borrowing, repayment and
                                        reborrowing during the period from the
                                        Tender Closing Date to the date
                                        thirty-three (33) months thereafter.

                  Termination:          The R/C Facilities shall terminate, and
                                        all outstanding R/C Loans shall be
                                        repayable in

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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.
<PAGE>
                                       5


                                        full, on the date three (3) years after
                                        the Tender Closing Date.

                  Purpose:              The proceeds of the R/C Loans shall be
                                        used (i) to refinance outstanding
                                        indebtedness of Asarco under the
                                        Existing R/C Facilities (as defined
                                        below) and in the event of an increase
                                        in the amount of the R/C Facilities
                                        above $250 million to repay a portion of
                                        outstanding A Tender Loans and (ii) for
                                        working capital purposes of Asarco. The
                                        "EXISTING R/C FACILITIES" means the
                                        credit facilities identified as such by
                                        Grupo Mexico and the Administrative
                                        Agent and which are on terms reasonably
                                        acceptable to the Arranger and Grupo
                                        Mexico. The aggregate principal amount
                                        of the Existing R/C Facilities is
                                        believed to total $800 million and to be
                                        for working capital purposes (based on
                                        publicly available information).

III.     CERTAIN PAYMENT PROVISIONS

         Fees and Interest Rates:       As set forth on Annex I.

         Optional Prepayments
         and Commitment Reductions:     All or a portion of the Loans may be
                                        prepaid at any time and the unutilized
                                        portion of the Facilities may be
                                        terminated in whole or in part (in
                                        minimum amounts to be agreed upon) at
                                        the respective Borrower's option
                                        (except, in the case of the R/C
                                        Facilities prior to the Tender Closing
                                        Date, at the option of Grupo Mexico). A
                                        Tender Loans once prepaid may not be
                                        reborrowed.

         Mandatory Prepayments and
         Commitment Reductions:         The A Tender Loans will be prepaid,
                                        undrawn commitments for A Tender Loans
                                        will be reduced and replaced, and R/C
                                        Loans will be prepaid, in that order, to
                                        the extent of the net cash proceeds
                                        received from the following (in each
                                        case subject to customary exclusions to
                                        be agreed):

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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.
<PAGE>
                                       6


                                        --        any asset sales by Asarco and
                                                  designated subsidiaries

                                        --        any debt issuances by Asarco
                                                  (other than R/C Loans, except
                                                  for R/C Loans required to
                                                  reduce the A Tender Facility)

                                        --        any equity issuances by Asmex
                                                  or Asarco (to any party other
                                                  than Asmex or Grupo Mexico)

                                        --        any sale of Asarco stock

                                        --        any proceeds received by
                                                  Asarco as a result of the
                                                  exercise (by holders) of
                                                  warrants relating to shares of
                                                  Grupo Mexico held in a trust
                                                  for the benefit of Asarco

IV.      GUARANTEES AND COLLATERAL

         Guarantees:                    (a) All obligations of Asmex (and, after
                                        the Merger, of Asarco) in respect of the
                                        A Tender Facility will be
                                        unconditionally guaranteed by Grupo
                                        Mexico.

                                        (b) All obligations of Asarco in respect
                                        of the R/C Facilities will be
                                        unconditionally guaranteed by Grupo
                                        Mexico until the A Tender Loans are
                                        repaid in full (except as otherwise
                                        noted below in the case of Alternative
                                        R/C Facilities, and provided the
                                        conditions for release of the collateral
                                        for such guarantee obligations have been
                                        met), and by Asmex until consummation of
                                        the Merger.

                                        The Borrowers and guarantors are
                                        collectively referred to herein as
                                        "CREDIT PARTIES."

         Collateral:                    (a) The obligations of Asmex in respect
                                        of the Facilities will be secured by a
                                        perfected first priority security
                                        interest in the Shares at any time owned
                                        by it.

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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.
<PAGE>
                                       7


                                        (b) The obligations of Grupo Mexico
                                        under its guarantees of the A Tender
                                        Facility and the R/C Facilities will be
                                        secured by a perfected first priority
                                        security interest in (1) shares of GMM
                                        representing 100% of the outstanding
                                        shares of GMM (other than shares not
                                        exceeding 1.50% held by others) and (2)
                                        all shares of Asarco held by Grupo
                                        Mexico, both immediately prior to the
                                        making of the A Tender Loans (presently
                                        representing approximately 9.8% of the
                                        outstanding shares of Asarco) and after
                                        the Merger. In addition, Grupo Mexico
                                        will covenant to maintain at all times,
                                        in support of its guarantees (so long as
                                        they remain in effect), an amount of
                                        unencumbered cash and short-term
                                        authorized money market investments (to
                                        be agreed with the Arranger, including
                                        deposits with approved banks, which in
                                        Mexico shall include only Banamex and
                                        Bancomer) equal to the lower of (A) 6
                                        months of interest on the outstanding A
                                        Tender Loans and (B) $100 million.

                                        (c) The obligations of Asarco in respect
                                        of the R/C Facilities will be secured by
                                        accounts receivable of Asarco (except as
                                        otherwise provided below in the case of
                                        "Alternative R/C Facilities").

                                        The security documentation will provide
                                        that in the event of default and
                                        enforcement or foreclosure at a time
                                        when both Asarco shares and GMM shares
                                        are held as collateral for the defaulted
                                        obligation, the collateral agent will be
                                        instructed to exercise reasonable
                                        efforts (for a period of up to 45 days)
                                        to sell collateral consisting of Asarco
                                        shares before selling collateral
                                        consisting of GMM shares.

        Certain Releases of Collateral: So long as no Default has occurred and
                                        is continuing:

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<PAGE>
                                       8


                                        (a) The pledge of Asarco Shares securing
                                        guarantees of the R/C Loans will
                                        terminate when the A Tender Loans are
                                        repaid in full, PROVIDED that at such
                                        time (i) the R/C Loans and R/C
                                        Facilities are not Alternative R/C Loans
                                        and Alternative R/C Facilities, and (ii)
                                        Asarco is in compliance with its
                                        financial covenant relating to minimum
                                        EBITDA;

                                        (b) The pledge of Asarco Shares securing
                                        guarantees of the Alternative R/C Loans
                                        will terminate when (i) the A Tender
                                        Loans are repaid in full, and (ii)
                                        Asarco's senior unsecured long-term
                                        indebtedness is rated at or above BBB-
                                        by S&P and Baa3 by Moody's;

                                        (c) The pledge of GMM shares securing
                                        Grupo Mexico guarantees of the
                                        Facilities will be reduced pro rata (on
                                        a percentage basis) with reductions (by
                                        repayment) of the outstanding principal
                                        of the A Tender Loans, PROVIDED that
                                        (except as described in clause (d)
                                        below) the percentage of outstanding GMM
                                        shares remaining in pledge as security
                                        for guarantees of the Facilities may not
                                        thereby be reduced below 51% (or such
                                        higher percentage, if any, as is
                                        required for approval of corporate
                                        actions of GMM that are subject to
                                        shareholder consent and for election of
                                        a majority of the Board of Directors of
                                        GMM);

                                        (d) At such time as the outstanding
                                        principal of the A Tender Loans has been
                                        reduced (by repayment) to an amount
                                        equal to or less than 25% of the
                                        original principal amount of the A
                                        Tender Loans, all GMM shares remaining
                                        in pledge as security for guarantees of
                                        the Facilities will be released,
                                        PROVIDED that Asarco's senior unsecured
                                        long-term indebtedness is rated at or
                                        above BBB- by S&P and Baa3 by Moody's.

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<PAGE>
                                       9


V.       CERTAIN CONDITIONS             The availability of the Facilities shall
                                        be conditioned upon satisfaction of,
                                        among other things, the following
                                        conditions precedent (the date upon
                                        which all such conditions precedent
                                        shall be satisfied and the A Tender
                                        Facility is first utilized being herein
                                        called the "TENDER CLOSING DATE") and
                                        the occurrence of the first utilization
                                        of the A Tender Facility on or before
                                        the date nine (9) months after September
                                        24, 1999, and other conditions precedent
                                        customary for facilities and
                                        transactions of this type, including
                                        evidence of authority and receipt of
                                        necessary consents and approvals:

                                        (a) Each Credit Party shall have
                                        executed and delivered satisfactory
                                        definitive financing documentation with
                                        respect to the Facilities (the "CREDIT
                                        DOCUMENTATION").

                                        (b) On or prior to the Tender Closing
                                        Date, cash in an amount not less than
                                        $270 million shall be contributed to the
                                        equity capital of Asmex through Grupo
                                        Mexico (i) from existing cash resources
                                        of GMM in an aggregate amount not less
                                        than $250 million, and (ii) from
                                        existing cash resources of Grupo Mexico,
                                        in an amount not less than $20 million;
                                        PROVIDED that in the event that Asmex
                                        requires cash in excess of such cash
                                        contributions and the A Tender Facility
                                        to consummate the Tender Offer, such
                                        additional cash shall be provided to
                                        Asmex through Grupo Mexico from other
                                        sources acceptable to the Arranger.

                                        (c) Satisfaction of the Arranger with
                                        all material terms and conditions of the
                                        Tender Offer and the definitive Merger
                                        agreement. In addition, the Tender Offer
                                        and the Merger shall have been, or shall
                                        be concurrently, consummated in a manner
                                        satisfactory to the Administrative Agent
                                        (including satisfaction of the
                                        Administrative Agent with all
                                        determinations as to the satisfaction of


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<PAGE>
                                       10


                                        material conditions thereunder) and no
                                        such condition of the Tender Offer or
                                        the definitive Merger agreement shall
                                        have been waived, amended, supplemented
                                        or otherwise modified without the prior
                                        written consent of the Administrative
                                        Agent; and Asmex shall have acquired
                                        shares of common stock of Asarco
                                        representing not less than 80% of the
                                        ordinary voting power of all of the
                                        shares of capital stock of Asarco on a
                                        fully diluted basis, including stock of
                                        Asarco owned by Grupo Mexico and
                                        subsidiaries prior to the Tender Offer
                                        (determined in a manner satisfactory to
                                        the Arranger).

                                        (d) Grupo Mexico and Asarco shall have
                                        entered into a definitive Merger
                                        agreement in form and substance
                                        satisfactory to the Administrative
                                        Agent, or Grupo Mexico shall have made
                                        satisfactory arrangements for the
                                        initiation of a statutory short-form
                                        merger, in each case pursuant to which
                                        Asarco will become a wholly-owned
                                        subsidiary of Grupo Mexico with Grupo
                                        Mexico able to exercise full control
                                        over the business and affairs of Asarco.

                                        (e) Invalidation or satisfaction of the
                                        requirements of Article 7 of Asarco's
                                        Restated Certificate of Incorporation
                                        with respect to the Transactions such
                                        that, following consummation of the
                                        Tender Offer, the Merger can be
                                        consummated without the affirmative vote
                                        of the holders of any Asarco shares
                                        other than Asmex; and invalidity,
                                        inapplicability or satisfaction (if
                                        necessary) of Article 10 of Asarco's
                                        Restated Certificate of Incorporation
                                        with respect to the Transactions or the
                                        Facilities.

                                        (f) Satisfaction or inapplicability of
                                        the requirements of Section 14A:10A of
                                        the New Jersey Business Corporation Act
                                        with respect to the Merger such that
                                        following

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<PAGE>
                                       11


                                        consummation of the Tender Offer the
                                        Merger can be consummated without the
                                        affirmative vote of the holders of any
                                        Asarco shares other than Asmex.

                                        (g) Invalidation, redemption or other
                                        inapplicability of the rights issued
                                        under Asarco's Shareholder Rights
                                        Agreement dated as of January 28, 1998,
                                        as amended.

                                        (h) There not being any statute, rule,
                                        regulation, judgment, order or
                                        injunction promulgated, entered,
                                        enforced, enacted, issued or applicable
                                        to the Tender Offer or the Merger by any
                                        domestic or foreign federal or state
                                        governmental regulatory or
                                        administrative agency or authority or
                                        court or legislative body or commission
                                        which (i) prohibits, or imposes any
                                        material limitations on, Grupo Mexico's
                                        or Asmex' ownership or operation of all
                                        or a material portion of Asarco's
                                        businesses or assets, (ii) prohibits, or
                                        makes illegal the acceptance for
                                        payment, payment for or purchase of
                                        Asarco common stock or the consummation
                                        of the Tender Offer or the Merger, (iii)
                                        results in a material delay in or
                                        restricts the ability of the Grupo
                                        Mexico, or renders Grupo Mexico unable,
                                        to accept for payment, pay for or
                                        purchase some or all of the tendered
                                        shares of Asarco common stock, or (iv)
                                        imposes material limitations on the
                                        ability of Asmex or Grupo Mexico
                                        effectively to exercise full rights of
                                        ownership of the Asarco common stock,
                                        including, without limitation, the right
                                        to vote the Asarco common stock
                                        purchased by it on all matters properly
                                        presented to Asarco's shareholders.

                                        (i) The Lenders, the Administrative
                                        Agent and the Arranger shall have
                                        received all fees required to be paid,
                                        and all expenses for which invoices have
                                        been presented, on or before the Tender
                                        Closing Date.

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<PAGE>
                                       12


                                        (j) The documents and materials filed
                                        publicly by Grupo Mexico (and its
                                        affiliates) and Asmex in connection with
                                        the Tender Offer shall have been
                                        furnished to the Administrative Agent
                                        and such documents and materials shall
                                        be reasonably satisfactory in form and
                                        substance to the Administrative Agent.

                                        (k) All regulatory and third party
                                        approvals and consents (including
                                        Hart-Scott-Rodino and other approvals
                                        and consents, if any) necessary in
                                        connection with the Transactions and the
                                        financing contemplated by the Second
                                        Amended and Restated Commitment Letter
                                        shall have been obtained and be in full
                                        force and effect and all applicable
                                        waiting periods shall have expired
                                        without any action being taken or
                                        threatened by any competent authority
                                        which could restrain, prevent or
                                        otherwise impose materially adverse
                                        conditions on the Transactions or the
                                        financing thereof, in each case on terms
                                        satisfactory to the Administrative
                                        Agent.

                                        (l) The Lenders shall have received (i)
                                        audited consolidated financial
                                        statements of Grupo Mexico, GMM and
                                        Grupo Ferroviario Mexicano, S.A. de C.V.
                                        ("RR") for the two most recent fiscal
                                        years (in the case of RR, one year)
                                        ended prior to the Tender Closing Date
                                        and (ii) unaudited interim consolidated
                                        financial statements of Grupo Mexico and
                                        of GMM for each quarterly period ended
                                        subsequent to the date of the latest
                                        financial statements delivered pursuant
                                        to clause (i) of this paragraph (l) as
                                        to which such financial statements are
                                        available.

                                        (m) The requisite Lenders shall be
                                        satisfied that upon making the initial A
                                        Tender Loans the requirements of
                                        Regulation U of the


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<PAGE>
                                       13


                                        Board of Governors of the Federal
                                        Reserve System shall have been complied
                                        with.

                                        (n) The Lenders shall have received such
                                        legal opinions (including opinions (i)
                                        from counsel to Grupo Mexico and its
                                        subsidiaries and (ii) from such special
                                        and local counsel as may be required by
                                        the Administrative Agent), documents and
                                        other instruments as are customary for
                                        transactions of this type or as they may
                                        reasonably request.

                                        (o) The negotiation, execution and
                                        delivery of definitive Credit
                                        Documentation with respect to the R/C
                                        Facilities satisfactory to all parties.
                                        Such Credit Documentation will contain a
                                        borrowing base condition to each
                                        utilization of the R/C Facilities,
                                        requiring that borrowings thereunder not
                                        exceed 85% of the amount of eligible
                                        receivables of Asarco securing the R/C
                                        Loans; provided that if such requirement
                                        renders the R/C Facilities initially
                                        unutilizable by Asarco in an amount
                                        sufficient to satisfy the financing
                                        needs of Asarco on the Tender Closing
                                        Date, such Credit Documentation will
                                        provide (until such time as such
                                        borrowing base and security requirement
                                        can be satisfied) for an alternative
                                        mechanism (referred to herein as the
                                        "ALTERNATIVE R/C FACILITIES") for
                                        utilization by Asarco of the R/C
                                        Facilities, with the following principal
                                        features (borrowings under such
                                        alternative mechanism being herein
                                        referred to as the "ALTERNATIVE R/C
                                        LOANS"):

                                        --        Alternative R/C Loans will not
                                                  be secured by Asarco assets

                                        --        Alternative R/C Loans will be
                                                  (i) guaranteed by Asmex (until
                                                  the Merger), with such
                                                  guarantee secured by the
                                                  Shares, and (ii) guaranteed by
                                                  Grupo Mexico,

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<PAGE>
                                       14


                                                  with such guarantee secured by
                                                  pledges of any Shares held by
                                                  Grupo Mexico and of the shares
                                                  of GMM; and such guarantee and
                                                  pledges will not terminate or
                                                  be fully released
                                                  (notwithstanding contrary
                                                  provisions elsewhere in this
                                                  Term Sheet) until (in addition
                                                  to other conditions noted
                                                  above) Asarco's senior
                                                  unsecured long-term
                                                  indebtedness is rated at or
                                                  above BBB- by S&P and Baa3 by
                                                  Moody's.

                                        In the event that the working capital
                                        requirements of Asarco may be satisfied
                                        with Existing R/C Facilities subsequent
                                        to the consummation of the Tender Offer,
                                        the aggregate principal amount of the
                                        R/C Facilities may be reduced by the
                                        amount of such Existing R/C Facilities.

                                        (p) Hedging arrangements satisfactory to
                                        the Administrative Agent shall have been
                                        entered into (with counterparties
                                        acceptable to the Administrative Agent)
                                        for a "costless" collar covering
                                        production of GMM (with a minimum copper
                                        price of $0.75/lb with respect to 70,000
                                        tons per annum) and, upon the
                                        consummation of the Tender Offer,
                                        covering production of Asarco (with a
                                        minimum copper price of $0.75/lb with
                                        respect to 100,000 tons per annum), in
                                        each case for a period of at least one
                                        year from the Tender Closing Date.

         On-Going Conditions:           The making of each extension of credit
                                        shall be conditioned on (a) the accuracy
                                        of all representations and warranties in
                                        the Credit Documentation (including,
                                        without limitation, the material adverse
                                        change and litigation representations)
                                        and (b) there being no default or event
                                        of default in existence at the time of,
                                        or after giving effect to the making of,
                                        such extension of credit.

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<PAGE>
                                       15


                                        As used herein and in the Credit
                                        Documentation a "MATERIAL ADVERSE
                                        CHANGE" shall mean (i) prior to the
                                        consummation of the Merger, any event,
                                        development or circumstance that has had
                                        or could reasonably be expected to have
                                        a material adverse effect on (a) the
                                        Transactions, (b) the business, assets,
                                        property or condition (financial or
                                        otherwise) of Grupo Mexico and its
                                        subsidiaries, GMM and its subsidiaries,
                                        or Asarco and its subsidiaries, in each
                                        case taken as a whole (including any
                                        material change, prior to consummation
                                        of the Tender Offer, in capital
                                        structure or indebtedness of Asarco and
                                        any material acquisition or divestiture
                                        of assets of Asarco or any of its
                                        subsidiaries taken as a whole, that in
                                        any such case has had or could
                                        reasonably be expected to have such a
                                        material adverse effect); PROVIDED,
                                        HOWEVER, that any adverse effect that
                                        copper prices have had or may have on
                                        the business, operations, property or
                                        financial condition of Grupo Mexico and
                                        its subsidiaries, GMM and its
                                        subsidiaries, or Asarco and its
                                        subsidiaries, in each case taken as a
                                        whole, shall not be deemed to have such
                                        a material adverse effect for purposes
                                        of this clause (i)(b), or (c) the
                                        validity or enforceability of any of the
                                        Credit Documentation or the rights and
                                        remedies of the Administrative Agent and
                                        the Lenders thereunder; and (ii) after
                                        the consummation of the Merger, any
                                        event, development or circumstance that
                                        has had or could reasonably be expected
                                        to have a material adverse effect on (a)
                                        the Transactions, (b) the business,
                                        assets, property, condition (financial
                                        or otherwise) or prospects of Grupo
                                        Mexico and its subsidiaries, GMM and its
                                        subsidiaries, or Asarco and its
                                        subsidiaries, in each case taken as a
                                        whole, or (c) the validity or
                                        enforceability of any of the Credit
                                        Documentation or the rights and remedies
                                        of

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<PAGE>
                                       16


                                        the Administrative Agent and the Lenders
                                        thereunder.

VI.    CERTAIN DOCUMENTATION MATTERS    The Credit Documentation for the A
                                        Tender Facility and the R/C Facilities
                                        shall contain representations,
                                        warranties, covenants and events of
                                        default customary for financings of
                                        these types and other terms deemed
                                        appropriate by the Lenders, including,
                                        without limitation (but subject in
                                        appropriate cases to customary and other
                                        exceptions to be agreed), those
                                        specified below.

       Representations and Warranties:  Financial statements (including pro
                                        forma financial statements); absence of
                                        undisclosed liabilities; no material
                                        adverse change; corporate existence;
                                        compliance with law; corporate power and
                                        authority; enforceability of Credit
                                        Documentation; no conflict with law or
                                        contractual obligations; no material
                                        litigation; no default; ownership of
                                        property; liens; intellectual property;
                                        no burdensome restrictions; taxes;
                                        margin stock regulations; Federal
                                        Reserve regulations; ERISA; Investment
                                        Company Act; subsidiaries; environmental
                                        matters; solvency; labor matters;
                                        accuracy of disclosure; and creation and
                                        perfection of security interests.

       Affirmative Covenants:           Delivery of financial statements,
                                        reports, accountants' letters, annual
                                        projections, officers' certificates and
                                        other information requested by the
                                        Lenders; payment of certain other
                                        obligations; all payments under the
                                        Facilities to be made free and clear of
                                        and without reduction by reason of
                                        present or future taxes (customary
                                        gross-up, indemnity and evidence of
                                        payment provisions); continuation of
                                        business and maintenance of existence
                                        and material rights and privileges;
                                        compliance with laws and material
                                        contractual obligations; maintenance of
                                        property and insurance; maintenance of
                                        books and records; right of


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<PAGE>
                                       17


                                        the Lenders to inspect property and
                                        books and records; notices of defaults,
                                        litigation and other material events;
                                        maintenance of required hedging
                                        arrangements; compliance with
                                        environmental laws; further assurances
                                        (including, without limitation, with
                                        respect to security interests in
                                        after-acquired property); ownership of
                                        GMM, of RR, of Asmex and, after the
                                        Merger, of Asarco; in the event of
                                        Asarco's utilization of the Alternative
                                        R/C Facility, Grupo Mexico to use its
                                        best efforts to cause Asarco to replace
                                        such utilization with R/C Loans that are
                                        not Alternative R/C Loans; and Grupo
                                        Mexico to use its best efforts to
                                        consummate the Merger as soon as
                                        practicable; and GMM to take reasonable
                                        steps to maintain investment grade
                                        ratings from S&P, Moody's and Duff &
                                        Phelps.

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<PAGE>
                                       18



         Financial Covenants:           Financial covenants relating to

                                        (a) Grupo Mexico (consolidated with all
                                        subsidiaries, and consolidated with all
                                        subsidiaries other than Southern Peru
                                        Copper Corporation)

                                                (i) Maximum Debt to EBITDA ratio

                                                (ii) Minimum ratio of EBITDA to
                                                interest expense

                                                (iii) Maximum Debt to Capital
                                                ratio

                                        (b) GMM and subsidiaries (for so long as
                                        any Grupo Mexico guarantee is in effect)

                                                (i) Debt to Capital ratio not
                                                exceeding 45%

                                                (ii) Minimum Tangible Net Worth

                                                (iii) Minimum Collections to
                                                Debt Service ratio

                                                (iv) Minimum annual level of
                                                export receivables

                                                (v) Minimum ratio of export
                                                receivables to SEN debt service

                                                (vi) Minimum ratio of EBITDA to
                                                interest expense

                                        (c) Asarco

                                                Minimum EBITDA levels

         Negative Covenants:            Limitations on: indebtedness (including
                                        preferred stock of subsidiaries);
                                        voluntary prepayments of indebtedness
                                        other than under the Facilities; liens
                                        (including negative pledge on stock of
                                        GMM, Asarco and RR); guarantee
                                        obligations; mergers, consolidations,
                                        liquidations and dissolutions; sales of
                                        assets; leases; capital expenditures;
                                        investments, loans and advances;
                                        dividends
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<PAGE>
                                       19


                                        and other payments in respect of capital
                                        stock; transactions with affiliates;
                                        sale and leasebacks; changes in fiscal
                                        year; and changes in lines of business.

        Special Covenant of Asmex:      Asmex shall covenant that it will not
                                        engage in any activity other than the
                                        Transactions, the A Tender Facility and
                                        activities necessary to effect the same.

         Events of Default:             (a) A Borrower shall fail to make any
                                        payment of principal of any Loan when
                                        due.

                                        (b) A Borrower shall fail to make any
                                        payment of interest or fees on any Loan,
                                        or any other payments required under the
                                        Credit Documentation, within 3 business
                                        days of due date.

                                        (c) Any representation or warranty by a
                                        Credit Party contained in the Credit
                                        Documentation or any certificate
                                        required to be delivered thereunder
                                        shall prove to have been incorrect in a
                                        material respect when made or deemed
                                        made.

                                        (d) A Credit Party (or any of its
                                        subsidiaries) shall fail to perform or
                                        observe any of its financial or other
                                        covenants under the Credit Documentation
                                        (subject to grace periods to be agreed).

                                        (e) Customary bankruptcy events of
                                        default, including (i) Grupo Mexico,
                                        GMM, Asarco or any of their subsidiaries
                                        (except for non-material subsidiaries
                                        (to be defined)) shall consent to the
                                        appointment of a receiver for itself or
                                        a substantial part of its property, (ii)
                                        Grupo Mexico, GMM, Asarco or any of
                                        their subsidiaries (except for
                                        non-material subsidiaries) shall seek
                                        relief under any applicable bankruptcy
                                        law or (iii) an involuntary bankruptcy
                                        or like proceeding shall have been
                                        commenced against Grupo Mexico, GMM,
                                        Asarco or any of their subsidiaries
                                        (except for non-material
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<PAGE>
                                       20


                                        subsidiaries) and such proceeding shall
                                        not have been stayed or vacated for a
                                        period of 60 days after the date it was
                                        commenced.

                                        (f) The security interest in any
                                        collateral furnished by a Credit Party
                                        listed above under "Guarantees and
                                        Collateral" shall cease to be a first
                                        priority perfected security interest as
                                        required hereunder.

                                        (g) Failure by a Credit Party to pay
                                        when due (after taking into account
                                        applicable grace periods) any unsecured
                                        or secured indebtedness (including
                                        capitalized lease obligations) or any
                                        default that permits the acceleration of
                                        the maturity of any such indebtedness
                                        and obligations or termination of any
                                        capital lease, aggregating in the case
                                        of all such indebtedness and obligations
                                        an amount equal to or exceeding
                                        threshold amounts to be agreed.

                                        (h) A final judgment or judgments for
                                        the payment of money shall be entered
                                        against Grupo Mexico, GMM, Asarco or any
                                        of their subsidiaries (except for
                                        non-material subsidiaries, and except,
                                        in the case of Asarco and its
                                        subsidiaries prior to consummation of
                                        the Tender Offer, judgments the
                                        existence of which was already disclosed
                                        and publicly available (or otherwise
                                        known by officers of the Arranger or
                                        Chase working on the Transactions) prior
                                        to September 24, 1999) in an aggregate
                                        amount for all such persons equal to or
                                        exceeding threshold amounts to be agreed
                                        and which have not been bonded, stayed
                                        or satisfied for a period of 30 days or
                                        more.

                                        (i) There shall occur one or more ERISA
                                        Events which individually or in the
                                        aggregate results in or could reasonably
                                        be expected to result in a material
                                        adverse change; or there shall exist an
                                        amount of unfunded benefit liabilities
                                        (as defined in the
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<PAGE>
                                       21


                                        Statement of Financial Accounting
                                        Standards No. 87), individually or in
                                        the aggregate for all Plans (excluding
                                        for purposes of such computation any
                                        Plans with respect to which assets
                                        exceed benefit liabilities), which could
                                        reasonably be expected to result in a
                                        material adverse change.

                                        (j) There shall occur a change in
                                        control of GMM, Asmex or (after the
                                        consummation of the Tender Offer)
                                        Asarco; or Persons (to be identified)
                                        controlling Grupo Mexico (I.E., having
                                        the power to elect a majority of the
                                        members of the Board of Directors of
                                        Grupo Mexico) on September 24, 1999,
                                        shall cease to maintain such control.

                                        (k) Default in the performance or
                                        observation of any term or condition in
                                        any material contract of Grupo Mexico,
                                        GMM or Asarco, or any of their
                                        subsidiaries, in each case taken as a
                                        whole, that could reasonably be expected
                                        to result in a material adverse change.

                                        (l) So long as any obligations under the
                                        A Tender Facility remain outstanding,
                                        any Default or acceleration under the A
                                        Tender Facility, or the R/C Facilities
                                        (including Alternative R/C Facilities)
                                        or the secured export note or other
                                        long-term debt obligations of GMM (with
                                        a threshhold amount, in the case of GMM,
                                        of $30 million).

         Voting:                        Amendments and waivers with respect to
                                        the Credit Documentation shall require
                                        the approval of Lenders holding not less
                                        than a majority of the aggregate amount
                                        of the Loans thereunder and commitments
                                        under the related Facilities, except
                                        that (a) the consent of each Lender
                                        directly affected thereby shall be
                                        required with respect to (i) changes in
                                        the maturity of any Loan,
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<PAGE>
                                       22


                                        (ii) reductions in the rate of interest
                                        or any fee or extensions of any due date
                                        thereof, (iii) increases in the amount
                                        or extensions of the expiry date of any
                                        Lender's commitment and (iv)
                                        modifications to the pro rata provisions
                                        of the Credit Documentation and (b) the
                                        consent of 100% of the Lenders shall be
                                        required with respect to (i)
                                        modifications to any of the voting
                                        percentages and (ii) releases of any
                                        guarantee other than of a non-material
                                        subsidiary (to be defined) or all or any
                                        substantial part of the collateral.

         Assignments and
         Participations:                The Lenders shall be permitted to assign
                                        and sell participations in their Loans
                                        and commitments, subject, in the case of
                                        assignments (other than to another
                                        Lender or to an affiliate of a Lender),
                                        to the consent of the Administrative
                                        Agent and Grupo Mexico (which consent in
                                        each case shall not be unreasonably
                                        withheld, provided that if a default
                                        shall have occurred and be continuing
                                        Grupo Mexico's consent shall not be
                                        necessary). In the case of partial
                                        assignments (other than to another
                                        Lender or to an affiliate of a Lender of
                                        any interest in the A Tender Facility),
                                        the minimum assignment amount shall be
                                        $5,000,000 unless otherwise agreed by
                                        Grupo Mexico and the Administrative
                                        Agent. Each assignment shall be subject
                                        to payment to the Administrative Agent
                                        of a processing fee of $3,500.
                                        Participants shall have the same
                                        benefits as the Lenders from which they
                                        acquired their participations with
                                        respect to yield protection and
                                        increased cost provisions. Voting rights
                                        of participants shall be limited to
                                        those matters with respect to which the
                                        affirmative vote of the Lender from
                                        which it purchased its participation
                                        would be required as described in items
                                        (a) and (b) of the paragraph on "Voting"
                                        above. Pledges of Loans in accordance
                                        with applicable law shall be permitted
                                        without restriction.
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<PAGE>
                                       23


         Yield Protection:              The Credit Documentation shall contain
                                        customary provisions (a) protecting the
                                        Lenders against increased costs or loss
                                        of yield resulting from changes in
                                        reserve, tax, capital adequacy and other
                                        requirements of law and from the
                                        imposition of or changes in withholding
                                        or other taxes and (b) indemnifying the
                                        Lenders for "breakage costs" incurred in
                                        connection with, among other things, any
                                        prepayment of a Eurodollar Loan (as
                                        defined in Annex I) on a day other than
                                        the last day of an interest period with
                                        respect thereto.

         Expenses and Indemnification:  The Borrowers shall pay (a) all
                                        reasonable out-of-pocket expenses of the
                                        Administrative Agent and the Arranger
                                        associated with the syndication of the
                                        Credit Facilities and the preparation,
                                        execution, delivery and administration
                                        of the Credit Documentation and any
                                        amendment or waiver with respect thereto
                                        (including the reasonable fees,
                                        disbursements and other charges of
                                        counsel) and (b) all out-of-pocket
                                        expenses of the Administrative Agent and
                                        (after an Event of Default) of the
                                        Lenders (including the fees,
                                        disbursements and other charges of
                                        counsel) in connection with the
                                        enforcement of the Credit Documentation.

                                        The Administrative Agent, the Arranger
                                        and the Lenders (and their affiliates
                                        and their respective officers,
                                        directors, employees, advisors and
                                        agents) will have no liability for, and
                                        will be indemnified and held harmless
                                        against, any loss, liability, cost or
                                        expense incurred in respect of the
                                        financing contemplated hereby or the use
                                        or the proposed use of proceeds thereof
                                        (except to the extent resulting from the
                                        gross negligence or willful misconduct
                                        of the indemnified party).

         Governing Law and Forum:       State of New York.
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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.
<PAGE>
                                       24




         Counsel to the Administrative
         Agent and the Arranger:        Milbank, Tweed, Hadley & McCloy LLP,
                                        and Ritch, Heather y Mueller S.C.




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[GRAPHIC OMITTED]                                     GRUPO MEXICO, S.A. DE C.V.


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