The U.S. military in the Philippines has been put on a "higher state of readiness" in case the rebellion against President Ferdinand Marcos jeopardizes Clark Air Base or the huge naval base at Subic Bay, Adm. William J. Crowe Jr., chairman of the Joint Chiefs of Staff, said last night.

"It's more of a heightened awareness" rather than an emergency reaction to the political crisis engulfing the Philippines, Crowe said in an interview. "We haven't seen any sign of a problem" in terms of anyone attempting to storm the bases or cut off communications.

Crowe said he was "optimistic" that U.S. interests will not be disrupted by the turmoil. He and other Pentagon leaders believe that only the communist New People's Army fighting a guerrilla war rather than the opposing political factions led by Marcos and Corazon Aquino pose a threat to the U.S. bases in the Philippines, which are the largest in the world outside the United States.

Crowe said he was taking a "wait-and-see" posture about what would happen in the Philippines in the next few days but indicated he felt the worst of the crisis had passed.

The State Department has been working on plans to extract Marcos from the Philippines, sources said, either by flying him out of the country on a U.S. plane or rendezvousing with him after the Philippine leader flies out of the country in his own plane.

As precautionary measures, U.S. forces in the Philippines have posted more guards around the bases and canceled leaves of service men and women, Pentagon officials said. They denied that U.S. forces had been put on a high state of alert for fear the bases would be attacked.

"We have not seen any real threat to the bases," said Crowe, adding that the American military presence in the Philippines had not even become "a heavy part of the dialogue" in the recent elections.

Although Clark Field and Subic Bay remained calm, several lawmakers renewed demands that the Pentagon look for alternative locations. "We can't assume we'll be able to stay there forever," Sen. Jim Sasser (D-Tenn.), ranking Democrat on the Senate Appropriations subcommittee on military construction, said yesterday.

Sasser stressed in an interview that he was not opposed to maintaining U.S. military presence in the Philippines but felt that the current turmoil there demands an insurance policy in the form of contingency plans.

"The Pentagon says there's no alternative to those bases," Sasser said. "But there's got to be an alternative if we're told to move out of them." He said he will press the Pentagon to deliver its study of alternatives to the Philippines bases by March 1.

Crowe said that the Pentagon will deliver the report, but added that alternatives to the present bases in the Philippines have been studied for years. The bottom line, the admiral said, is that it "would be difficult and expensive" to put U.S. ships and planes somewhere else in the Pacific.

Crowe, who until five months ago was the senior U.S. commander in the Pacific, said that the increasing Soviet naval presence at Camranh Bay in Vietnam makes the U.S. air and naval presence in the Philippines more crucial than ever.

The Central Intelligence Agency recently drew up two lists of countries that were of vital importance to the strategic interests of the United States, sources said. One list ranked the nations in order of their strategic location; a second list ranked them in order of political instability. The Philippines, sources said, ranked first on both lists.

While calling the situation in the Philippines "still dicey," Crowe said he was "fundamentally optimistic" about both the short-term and long-term prospects for the stability of the nation as well as the American presence there.