Exhibit 10(b)



                                         December 23, 1984



         Phillips Petroleum Company
         Phillips Building
         Bartlesville, OK 74004

         Attn:      William C. Douce,
                    Chairman of the Board
                    and Chief Executive Officer

         Gentlemen:

                    Each of the undersigned (the "Mesa Entities")
         hereby agrees, on the one hand, and by acceptance hereof
         Phillips Petroleum Company (the "Company") hereby agrees, on
         the other hand, that, subject to his or its own right to
         pursue his or its own legitimate business objectives
         independently and in good faith, (i) he or it and his or its
         affiliates will continue to do business with the other and with
         the other's directors, affiliates and associates and the
         affiliates and associates of the other's directors (collectively,
         "Related Parties") in the ordinary course and that the
         events relating to the Mesa Entities' attempt to acquire
         control of the Company and the Company's response thereto
         that have preceded this letter agreement will not be taken
         into account in making decisions with respect to business
         relations between them and (ii) he or it will not, and will
         not permit his or its affiliates to, directly or indirectly,
         take any action to, or encourage any other person or entity
         to, interfere with or adversely affect the business activities,
         contractual relationships or business opportunities of the
         other and the other's Related Parties.

                   This letter agreement shall be construed independ-
         ently of, and any breach hereof shall not affect any obligation
         of any party under, the separate agreement between us dated
         the date hereof.  Such obligations under said separate
         agreement shall remain in full force and effect despite any
         claimed breach of this letter agreement.


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                     This letter agreement shall be governed and construed
          in accordance with the laws of the State of Delaware.  Any
          actions, causes of action or suits which may hereafter be
          commenced by virtue of this letter agreement may only be
          brought in a federal or state court located in the State of
          Delaware and each party hereto agrees to submit to the
          jurisdiction of any such court in any such action, cause of
          action or suit which may be commenced by any other party
          hereto.

                    This letter agreement may be executed in two or
          more counterparts which together shall constitute a single
          agreement.

                                   Very truly yours,

                                   MESA PARTNERS:


                                   By: Mesa Asset Co., General Partner

                                   By /s/ David H. Batchelder
                                     --------------------------------


                                   By:  Cy-7. Inc., General Partner

                                   By /s/ Joel L. Reed
                                     --------------------------------

                                   and

                                   By: Jack-7, Inc.,  General Partner

                                   By /s/ Joel L. Reed
                                     --------------------------------


                                   MESA PETROLEUM CO.

                                   By /s/ David H. Batchelder
                                     --------------------------------


                                   MESA ASSET CO.

                                   By /s/ David H. Batchelder
                                     --------------------------------



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                                   WAGNER & BROWN
                                   WAGNER & BROWN II
                                   and
                                   BROWN & WAGNER

                                   By:  Cyril Wagner, Jr., General Partner

                                   By: Jack E. Brown, General Partner


                                   By /s/ Joel L. Reed
                                     --------------------------------
                                     Joel L. Reed, Attorney-in-Fact


                                   JACK-7, INC.

                                   By /s/ Joel L. Reed
                                     --------------------------------


                                   CY-7, INC.

                                   By /s/ Joel L. Reed
                                     --------------------------------


                                   Jack E. Brown,
                                      in his individual capacity


                                   By /s/ Joel L. Reed
                                     --------------------------------
                                     Joel L. Reed, Attorney-in-Fact


                                   Cyril Wagner, Jr.,
                                      in his individual capacity


                                   By /s/ Joel L. Reed
                                     --------------------------------
                                     Joel L. Reed, Attorney-in-Fact





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                                     /s/ T. Boone Pickens Jr.
                                     --------------------------------
                                     T. Boone Pickens Jr.,
                                      in his individual capacity



          ACCEPTED AND AGREED AS OF THE
          DATE WRITTEN ABOVE:

          PHILLIPS PETROLEUM COMPANY


          By
            ---------------------------------








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<PAGE>




                                     --------------------------------
                                     T. Boone Pickens Jr.,
                                      in his individual capacity



          ACCEPTED AND AGREED AS OF THE
          DATE WRITTEN ABOVE:

          PHILLIPS PETROLEUM COMPANY


          By  /s/ W.C. Douce
            ---------------------------------








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