WASHINGTON (AP) _ The Exxon Corp. told Congress on Friday it is committed to any ''reasonable'' continuation of the Alaska oil spill cleanup next spring. President Bush said he would do his best to make sure Exxon doesn't ''pull back on an agreement.''

Exxon officials testified the company intends to suspend cleanup activities in September because of oncoming winter weather and would return to see if more work is necessary in the spring.

But a top U.S. Coast Guard official said he expects ''disagreements on what should be done'' next year, with no clear consensus on how free of oil the stretches of rocky Alaska shore must be before being declared clean.

Exxon's plans in the cleanup of more than 700 miles of shoreline, damaged by the Exxon Valdez tanker spill last March, came under scrutiny this week with the disclosure of an internal company memorandum which said ''no commitment should be made'' on the timing of suspending or resuming cleanup operations.

Asked by reporters about the matter at a White House news conference Friday - hours after Exxon officials testified on Capitol Hill - Bush made clear he considers Exxon to have made a commitment to stay with the cleanup.

''If I had the feeling Exxon was going to pull back on an agreement or fail to fulfill an agreement they'd made with us, with the government, or with the state of Alaska, I would be very much exercised and try my best to do something about it,'' said the president.

Alaska officials publicly interpreted the July 19 Exxon memo as an indication the company was preparing to pull out of a cleanup effort that was far from completed. The brouhaha prompted Friday's hearing by the Interior Subcommittee on Water, Power and Offshore Energy Resources, during which Exxon was asked to detail its intentions.

The memo, written by the manager of Exxon's cleanup operation in Alaska, ''suggests Exxon is putting together its plan for demobilization without Coast Guard approval,'' said Rep. George Miller, D-Calif., chairman of the subcommittee.

W.D. Stevens, president of Exxon Co. USA, said the wording of the memo was ''unfortunate.''

He said the company will withdraw its equipment and estimated 10,000 workers from the contaminated region beginning Sept. 15 because of potential safety problems with rough seas and weather. But he said Exxon would ''return to the areas in the spring of 1990 to reinspect the area, to assure that the job has been properly done, and if not, to put it right.''

Pressed by Miller on whether Exxon plans to resume cleanup operations in the spring, Stevens said he could not give ''an unequivocal commitment'' and added, ''I think it would be naive to do that.''

''We will follow through on any reasonable request that is made (by the U.S. Coast Guard),'' said Stevens, adding that there likely will be ''scientific disagreement'' over what areas are clean and whether further work is needed.

Coast Guard Vice Admiral Clyde Lusk told the subcommittee that a working group of federal and state officials as well as various scientists and representatives from Exxon will participate in the inspection next spring.

But Lusk acknowledged that while the Coast Guard can ask Exxon to perform additional cleanup at a specific site, it has no authority to require the company to do so.

''I have absolutely no doubt there are going to be disagreements over what should be done'' in terms of continuing the cleanup efforts, he said.

''What is clean?'' Lusk asked rhetorically at another point. ''I don't know how we're going to make that decision.''

The potential for sharp disagreement over when a stretch of shoreline should be considered cleaned became evident at Friday's hearing.

Exxon executives contended that about 600 miles of contaminated shoreline already had been treated, while Alaska's chief environmental official put the number at about 190 miles and said in many cases oil has seeped back into the rocks and pebbles.

''We cannot imagine how Exxon can conclude 600 miles have been treated,'' Dennis Kelso, the commissioner of Alaska's Department of Environmental Conservation, told the House panel. ''If that statement were made in Kodiak or Homer the roof would rise. Maybe they're looking at a different gulf.''