The Bush administration is ready to begin phasing out the U.S. military bases in the Philippines, acknowledging for the first time that the end of the Cold War has lessened the need for the facilities, informed administration and congressional sources said yesterday.

With negotiations on the bases scheduled to begin Tuesday in Manila, U.S. negotiators will seek a phaseout period that could last up to 10 years, followed by continued military access to the facilities, perhaps on a commercial basis, after the last American forces depart, according to officials familiar with the U.S. negotiating stance.

They said it remains particularly important for the United States to maintain access to the Crow Valley training range where U.S. pilots and allied air forces now train.

The officials said the United States will not propose a definite timetable for departing from the facilities -- Clark Air Base in Angeles City, Subic Bay Naval Base in Olongapo and four smaller installations. Throughout the post-war era, the military installations have been a key staging area for U.S. forces in the Western Pacific. But in recent years, rising Philippine nationalism has made the U.S. presence a bilateral irritant.

The officials said the U.S. negotiating panel will stress the need for a gradual withdrawal to allow sufficient time for the Philippine government to prepare alternative plans for the bases and to cushion what is expected to be another blow to the already staggering Philippine economy.

The lengthy phaseout is intended in part to minimize the cost of relocating the 16,000 U.S. troops now in the Philippines and also to give Washington's regional allies more time to adjust to what will be the most significant security realignment in Southeast Asia since the American retreat from Vietnam in 1975.

Officials here preparing for the talks said the new U.S. proposal for phasing out the facilities reflects a dramatic shift in thinking within the administration brought on by the end of the Cold War and the dawning of a new Soviet-American partnership. Where the bases were once considered an invaluable deterrent to a perceived Soviet threat to Southeast Asian security, officials now concede that the era of a large-scale U.S. military presence in the Philippines is drawing to a close.

"The world is changing," one administration official said. "Those bases are not as valuable as they used to be."

The proposal for a phaseout closely matches the idea of some prominent Philippine government leaders, notably Defense Secretary Fidel V. Ramos, who has said that all U.S. forces should be removed from the Philippines by June 12, 1998, the centennial of the country's symbolic declaration of independence from Spain by President Emilio Aguinaldo.

By proposing a phaseout -- which U.S. officials prefer to call a "phase down" -- the administration appears to have cleared the way for a smoother round of talks, which were expected to be rancorous and to further inflame anti-American sentiment. The debate now can be shifted from whether U.S. forces should be withdrawn to the timing and mechanics of the departure, officials here said.

The bases had become a major irritant in U.S.-Philippine relations under the government of President Corazon Aquino, as a more vocal nationalist minority has stepped up demands for their removal. Philippine opponents of the bases see them as the last vestige of U.S. domination of a former colony, and an infringement on Philippine sovereignty.

However a huge majority of Filipinos still support a continued U.S. presence, a sentiment that has increased in the weeks since a devastating earthquake struck the main island of Luzon and American personnel from the bases pitched in with a massive and visible rescue effort. The U.S. Embassy says its most recent polls show two of three Manilans surveyed favored keeping the bases. That pro-base sentiment is believed to be even higher in the provinces outside Manila.

Rep. Stephen J. Solarz (D-N.Y.), chairman of the House Foreign Affairs subcommittee on Asian and Pacific affairs and a frequent visitor to the Philippines, said in an interview Tuesday that he was aware of the administration's changed posture going into the talks. "I would not be surprised to find an agreement in which our presence is phased out," Solarz said. "I would like to see an arrangement where we can continue to use those facilities on a commercial basis."

As evidence of the reduced need for the bases, officials here noted that in the current U.S. military buildup in the Persian Gulf, the Philippine bases have not been used. The troops and supplies on the way to the gulf passed through a U.S. facility at Diego Garcia, while some have passed through Singapore.

Singapore and the tiny neighboring country of Brunei have opened facilities to U.S. troops, further reducing the need to maintain a large-scale and permanent American presence in the Philippines, officials said.

The United States and Singapore are close to an agreement to allow a small U.S. squadron to be stationed on that island city-state. In Jakarta, Indonesia, last July, a senior State Department official disclosed that Brunei had made a similar offer to host a small contingent of U.S. forces, but so far, the United States has not asked to place troops there, officials said.