The Bush administration said yesterday it is prepared to abandon the big U.S. naval base in the Philippines rather than offer new concessions to reverse a preliminary vote in the Philippine senate to shut it down.

Washington officials said the end may be near for the nearly century-long U.S. military presence in the strategic islands, and a crisis at hand for U.S.-Philippine relations.

"We've made our best offer," President Bush said several hours after the 12 to 11 Philippine Senate vote against continuing U.S. use of Subic Bay Naval Base, previously considered one of the most important U.S. overseas facilities. "There will be no change on the part of United States," Bush added.

Secretary of Defense Richard B. Cheney called the vote in Manila "extremely unfortunate" and "a real tragedy for the Philippines," but said in an early morning interview with Cable News Network that if the base accord is terminated, "We'll pack up and leave, that's it."

Behind the stiff U.S. attitude toward the news from Manila was a greatly diminished military requirement for the base in view of the end of the Cold War and the disintegration of the Soviet Union, and the belief that shock treatment rather than offers of increased U.S. aid was the only hope for a reversal of yesterday's vote.

The accord worked out this summer after years of negotiations would permit the United States to retain use of Subic for a minimum of 10 years in return for at least $203 million yearly, plus millions more in potential additional benefits not specified in the pact.

Ratification requires approval by two-thirds, or 16 members, of the 23-member Senate. The vote in Manila yesterday took place as the Senate was formed as a committee, and thus was not final. The tally indicated, however, that major shifts in position would be necessary to approve the pact.

Some administration officials expressed the view that the Senate will reverse course when it realizes that the Americans actually are going to leave and U.S. military aid will cease. President Corazon Aquino is planning a massive pro-base rally to mobilize public opinion, a majority of which is believed to favor continuation of the bases agreement.

The predominant reaction here, however, was that a reversal of the senate position was unlikely in the short run, and that the long run may be too late to head off the dismantling of the big U.S. naval base. Earlier this summer Clark Air Base north of Manila, the largest U.S. military base overseas, was ordered closed because of the devastation caused by the eruption of nearby Mount Pinatubo and the prospect that the volcano could continue to erupt.

Since Commodore George Dewey sailed into Manila Bay to vanquish the occupying Spanish fleet in 1898, a military position in the Philippines has been important to U.S. power in the Pacific.

The U.S. occupation was loosened in the 1930s, and the Philippines was given full independence in 1946 after Filipinos and Americans fought together against the Japanese in World War II. The big U.S. bases remained under a series of negotiated accords between Washington and Manila, but they became increasingly unpopular with Filipino nationalists who saw them as symbols of colonialism, dependency and victimization.

"For all practical purposes the treaty is defeated," said Senate President Jovito Salonga, an outspoken opponent of the accord, according to the Associated Press. "This is the final act -- the entombment of the father image of America in this country," said Aquilino Pimentel, who also voted against the agreement.

On the other hand, pro-bases senators were quoted as saying they have not abandoned the drive to obtain ratification. Some media reports suggested Manila will now attempt to win concessions in renewed bargaining with Washington, but the reaction of Bush and other officials indicated this is not likely to succeed.

Apparently as a result of the vote, share prices on the Manila stock exchange fell more than 4 percent during the day. U.S. officials said they expect major economic repercussions in a country where U.S. military procurement, payrolls and related spending are major items. Foreign investment and debt restructuring as well as modernization of the Philippine military could also be drastically affected, analysts said.

Sen. Richard G. Lugar (R-Ind.), a leading advocate of aid to the Philippines since the 1986 "people power" revolution that ousted President Ferdinand Marcos and brought Aquino to power, said rejection of the bases agreement would be "a historic tragedy" for the Philippines, with serious repercussions in congressional and public opinion in this country. Lugar said "a good number of other countries are eyeing the money that would be freed up" if the United States no longer is committed to supply base-related aid to Manila.

Cheney and other Pentagon officials took the news calmly, insisting that the United States will be able to find satisfactory substitutes for the military support long provided by the Philippine bases. Until a few years ago, Subic and Clark were considered of such vital importance to U.S. military activities in the Pacific and Indian oceans that abandoning them was almost unthinkable. This attitude shifted notably with changes in world conditions and increased political opposition to the bases in Manila.

A senior Defense Department official said late last week that if ordered to vacate Subic, the Navy will move "in bits and pieces" from there to other places in the Pacific or at home. The main substitute for Subic's ship repair facilities, the largest in Asia, is likely to be Yokosuka Naval Base near Yokohama, Japan, he said. The Japanese government has agreed to pay all labor costs for U.S. military needs, so ship repair may actually be cheaper for the Navy there than in the Philippines, the official said.

Cheney said the loss of Subic would probably bring an increased level of activity for the U.S. facilities at Guam, which is a U.S. territory.