EXHIBIT 99.A

                           CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                       AS ADOPTED PURSUANT TO SECTION 906
                        OF THE SARBANES-OXLEY ACT OF 2002

         In connection with the Quarterly Report on Form 10-Q for the period
ending March 31, 2003, of El Paso Natural Gas Company (the "Company") as
filed with the Securities and Exchange Commission on the date hereof (the
"Report"), I, John W. Somerhalder II, Chairman of the Board and Chief Executive
Officer, certify (i) that the Report fully complies with the requirements of
Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended, and
(ii) that the information contained in the Report fairly presents, in all
material respects, the financial condition and results of operations of the
Company.




                                             /s/ John W. Somerhalder II
                                             ----------------------------------
                                             John W. Somerhalder II
                                             Chairman of the Board and
                                             Chief Executive Officer
                                             (Principal Executive Officer)

                                             May 14, 2003

A signed original of this written statement required by Section 906 has been
provided to El Paso Natural Gas Company and will be retained by El Paso Natural
Gas Company and furnished to the Securities and Exchange Commission or its
staff upon request.