Exhibit 10.17.4

EXHIBIT A

AMENDMENT TO TRUST AGREEMENT

Effective May 3, 1999, Attachment I, List of Arrangements to the Trust Agreement
between Phillips Petroleum Company and Wachovia Bank, N.A., as Trustee dated as
of June l, 1998 (the “Trust Agreement”), is hereby amended to read as set forth
below:

ATTACHMENT I

List of Arrangements

Key Employee Deferred Compensation Plan of Phillips Petroleum Company

Phillips Petroleum Company Supplemental Executive Retirement Plan

Key Employee Supplemental Retirement Plan of Phillips Petroleum Company

Defined Contribution Makeup Plan of Phillips Petroleum Company

Kev Employee Missed Credited Service Retirement Plan of Phillips Petroleum
Company

Principal Corporate Officers Supplemental Retirement Plan of Phillips Petroleum
Company

Annuity payments all in payout status

Supplemental Retirement

Annuity payments all in payout status accrued as a result of participation in
the Phillips Petroleum Company Key Employee Death Protection Plan and the
individual contracts for deferred compensation

Phillips Oil Company Excess Benefit Plan

One remaining participant in annuity payout

Aminoil Retirement Contracts

Contracts with [redacted] and [redacted]—both in annuity payout status    

Phillips Petroleum Company Executive Severance Plan”

The Trust Agreement is in all other respects ratified and confirmed without
amendment. Each of the parties to the Trust Agreement has caused this Amendment
to be executed on its behalf by its duly authorized officer, as of May 3, 1999.

 

Phillips Petroleum Company    Wachovia Bank, N.A. By:    /s/ T.C. Morris    By:
   /s/ Joe O. Long Title:    Sr. Vice President & Chief Financial Officer   
Title:    Sr. Vice President