U.S. and Philippine negotiators agreed Saturday on terms for the continued operation of strategic U.S. military facilities in the Philippines for the next two years and plan to sign an accord at the State Department Monday, administration officials said last night.

The accord, under negotiation since April, will provide $481 million in U.S. compensation in 1989 and 1990, up sharply from the current $180 million per year for use of Clark Air Base and Subic Bay Naval Base. They are the largest U.S. military facilities overseas and among the most important in the world.The Philippines had been asking for $1.2 billion annually, but Washington had said consistently that such large sums could not be provided in an era of U.S. budget ceilings.

In the end, Philippine negotiators said they would settle for a Reagan administration statement that the next U.S. administration will seek to help Manila reduce a $28 billion external debt by creative uses of the proceeds from a Multilateral Aid Initiative (MAI) that the United States, Japan and other countries are planning for the Philippines next year.

The wording of the U.S. statement on debt reduction was still under discussion among U.S. departments and agencies Saturday. An informed official said it was expected, but not yet certain, that interagency agreement on this point would permit the ceremonial signing of a "memorandum of agreement" on the bases by Secretary of State George P. Shultz and Philippine Foreign Minister Raul Manglapus at the State Department Monday.

As a concession to the Philippines, the administration agreed to speed delivery of some U.S. aid that was previously appropriated but not disbursed. Some of the aid will be made available in cash to facilitate quick spending, a U.S. official said.

The breakthrough in the often contentious negotiations, first reported by The New York Times, got a strong push in repeated unannounced meetings here this week between Manglapus and Assistant Secretary of State Gaston Sigur. In meetings of lower-level officials Saturday, Philippine negotiators said they are ready to sign the accord being discussed.

The negotiations are technically a review of the U.S.-Philippine Military Base Agreement, which expires in 1991.

Large stockpiles of fuel and ammunition are maintained at Clark Air Base, from which the United States can stage airlift operations and train combat pilots in the 13th Air Wing based there. Subic Bay Naval Base is the main rest and repair stop for the U.S. fleet operating from the mid-Pacific to the Persian Gulf.

Because of the difficulty of reaching aggrement on the bases review and doubts about renewal of the broader pact, the Pentagon for the first time seriously contemplated arrangements under which U.S. forces would go elsewhere in the Pacific for support.