Magellan Midstream Partners (MMP) 10-Q 2003 Q2 Quarterly report

Exhibit 32.1

The following certification shall not be deemed “filed” for purposes of Section 18 of the Exchange Act or otherwise subject to the liability of that section. Such certification will not be deemed to be incorporated by reference into any filing under the Securities Act or the Exchange Act, except to the extent that the registrant specifically incorporates it by reference.

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 of Williams Energy Partners L.P. (the “Partnership”) on Form 10-Q for the period ending June 30, 2003 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Don R. Wellendorf, Chief Executive Officer of WEG GP LLC, the General Partner of the Partnership, certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that:

(1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and result of operations of the Partnership.

/s/ Don R. Wellendorf    

Don R. Wellendorf, Chief Executive Officer

Date: August 14, 2003

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