WASHINGTON – On the brink of war, President Bush and summit partners from Britain and Spain gave the United Nations a Monday deadline to endorse the use of force to compel Iraq’s immediate disarmament.

“Tomorrow is a moment of truth for the world,” said Bush, commander-in-chief of 250,000 troops ringing Iraq and ready to act with or without U.N. approval. He spoke Sunday after an Atlantic island summit with British Prime Minister Tony Blair and Spanish Prime Minister Jose Maria Aznar.

Though the leaders pledged to seek compromise with U.N. foes through the night and all day Monday, they offered little hope of a diplomatic breakthrough. Even if a compromise plan somehow secured approval of a U.S.-Britain-Spain resolution at the U.N., it would delay military action only a week or so, officials said.

Bush suggested the resolution might not even be put to a vote.

“If Saddam refuses even now to cooperate fully with the United Nations, he brings on himself the serious consequences,” the leaders said in a joint statement. They went on to list their plans for Iraq after hostilities, including repairing damage that might be caused by Saddam Hussein and preserving oil and other natural assets.

The leaders gathered with more than 250,000 troops, a naval armada and an estimated 1,000 combat aircraft positioned in the Persian Gulf area, an American-led force ready to strike if and when the president gives the word.

“The Iraqi regime will disarm itself or the Iraqi regime will be disarmed by force,” Bush said.

The summit, held at a U.S. military base on this dot in the eastern Atlantic, amounted to less than two hours of talks. No more was needed, U.S. officials said, because the conclusion was preordained.

Even as they flew to a meeting billed as a last-ditch bid at diplomacy, Bush and his advisers worked on a major war address that he could deliver as early as Monday night. The speech would give Saddam a final ultimatum to disarm or face war, probably within days, senior U.S. officials said.

At a post-summit news conference, Bush urged other nations to support “the immediate and unconditional disarmament” of Iraq.

France, Germany and Russia have opposed an additional United Nations resolution to set an ultimatum for the Iraqi leader to disarm — and the French have threatened to veto it. Efforts to win the votes of uncommitted nations at the U.N. Security Council have faltered in recent days.

Blair, under the most domestic pressure to get U.N. backing, accused the resolution’s opponents of weakening the alliance against Saddam.

“I have to say that I really believe that had we given that strong message some time ago, Saddam might have realized that the games had to stop,” the prime minister said.

Aznar, the prime minister of Spain, where millions of protesters staged rallies Friday, said he was not dissuaded by dissent.

“We are well aware of the international world public opinion, of its concern, and we are also very well aware of our responsibilities and obligations,” Aznar said.

Portugal Prime Minister Jose Durao Barroso called the Azores summit “the last chance of a political solution. It may be a small chance but if there is only one chance in a million it’s worth trying this opportunity.”

Far from this lush Portuguese archipelago, Saddam warned that if Iraq is attacked, it would take the war anywhere in the world “wherever there is sky, land or water.”

At the United Nations, chief weapons inspector Hans Blix was working on the details of a plan envisioning that inspections would continue for months. He was scheduled to present it to the Security Council on Tuesday.

Even so, U.N. weapons inspectors bracing for war flew most of their helicopters out of Iraq, and Germany advised its citizens to leave the country immediately.

Bush was expected to issue a similar warning to humanitarian workers and journalists in his upcoming speech, dubbed “the ultimatum address” inside the White House.

The president laid the choice at Saddam’s feet.

“The decision is his to make. It’s been his to make all along, as to whether or not there’s the use of military,” the president said. “He got to decide whether he’s going to disarm, and he didn’t. He can decide whether he wants to leave the country.”

Those were the only two alternatives to war offered by Bush, and neither was likely to occur, officials said.

In a flash of frustration, Bush jumped in to field a question posed to Aznar about a new U.N. resolution.

“We do have resolution,” the president snapped. Punching the air with his fist, he referred to last fall’s unanimous vote to disarm Iraq and said: “The United Nations Security Council looked at the issue four and a half months ago and voted unanimously to say, `Disarm immediately and unconditionally, and if you don’t, there are going to be serious consequences.’ The world has spoken, and it did in a unified voice.”

Then he apologized to Aznar for answering the question.

Later, Bush said the U.N. “didn’t do its job” to stop bloodshed in Rwanda or Kosovo. “We hope tomorrow the U.N. will do its job. If not, all of us need to step back and try to figure out how to make the U.N. work better, as we head into the 21st century.”

Maybe the U.N. could make amends, he said, by helping rebuild Iraq after Saddam is gone.

Bush waffled on his recent promise to put the second resolution to a vote at the U.N. whether or not it was doomed to fail.

“France showed their cards” by pledging to veto any resolution that contained a war-making ultimatum, he said.

U.S. officials said the three leaders were unlikely to seek a vote if it was likely to fail, because rejection would undermine their argument that war without U.N. authority was legal.

In Washington, Vice President Dick Cheney underscored Bush’s frustration with Paris by saying, “It’s difficult to take the French serious.” He rejected a proposal by French President Jacques Chirac to impose a 30-day deadline for Iraq to disarm.

Two thousand miles away, Bush was asked whether the diplomatic window would be closed Monday. “That’s what I’m saying,” he replied.

One senior U.S. official said that in his remarks, Bush did not intend to rule out a possible compromise that would briefly extend a March 17 deadline written into the resolution that has stalled at the U.N. This official added, though, that any new resolution must be backed by a threat of force, something France has opposed.