The Bush administration insisted that the U.N. Security Council vote this week on a revised resolution. Under this resolution, the United States would extend a proposed March 17 deadline for Hussein to disarm.
It would also set "benchmarks" specifying the compliance Iraq would have to show by certain dates.
But U.S. officials said they would refuse to stretch a deadline for Iraq by more than a few days. The United States quietly rebuffed efforts by Britain to give Iraq until the end of this month to comply.
Canada proposed pushing back a deadline by three weeks - extending the process into next month. By late yesterday, the United States and Britain had not settled on a revised resolution.
"The vote will take place this week," said Ari Fleischer, President Bush's spokesman. "There's room for a little more diplomacy here but not much room and not much time."
Fleischer rejected as a "nonstarter" a proposal by the six uncommitted countries on the Security Council to extend the deadline by as much as 45 days.
The high-stakes diplomacy went on as more than 200,000 U.S. troops stood poised in the Persian Gulf region.
Under extraordinary pressure at home, Prime Minister Tony Blair of Britain is desperate to secure U.N. authorization for a war against Iraq. Opposition in Britain to a war without U.N. approval is so strong in his Labor Party that some express the fear it could topple Blair from power.
Another supporter of a U.S.-led invasion of Iraq, Prime Minister Jose Maria Aznar of Spain, which is on the Security Council, also faces intense public opposition to a war.
British diplomats are working feverishly to craft a resolution that could win the nine Security Council votes required for approval. Authorization by the council would demonstrate broad international backing for military action, even if France or Russia vetoed the resolution, as they have threatened to do.
But diplomats at the United Nations expressed fear yesterday that President Bush, who spoke with Blair by phone Monday night, would refuse to make the compromises needed to secure the additional votes.
U.S. officials, deeply skeptical that Iraq would fully disarm as long as Hussein holds power, have made clear that they are continuing to seek backing from the United Nations mostly to shore up the beleaguered Blair.
"We're hanging on to diplomacy," a U.S. official said yesterday, "because of the need to give credence to Blair's promise to pursue diplomacy as far as he could. It's not in our interest to have Tony Blair fall as prime minister over his commitment to help us."
Defense Secretary Donald H. Rumsfeld went so far yesterday as to suggest that Britain, which has dispatched more than 40,000 troops to the Persian Gulf, might not join the United States in a war against Iraq. Rumsfeld said he had spoken an hour before with Britain's defense minister, Geoffrey Hoon.
Later, after the British prime minister's office insisted that "nothing has changed" in Britain's commitment to the U.S.-led war effort, Rumsfeld issued a statement saying, "In the event that a decision to use force is made, we have every reason to believe there will be a significant military contribution from the United Kingdom."
Some say Blair is gambling his political career with his staunch support for the United States at a time when American foreign policy is profoundly unpopular in his country. While fighting to preserve his standing at home, Blair is trying to persuade Bush to steer a course that other members of the Security Council can support.
At the same time, the British prime minister is trying to preserve the authority of the United Nations. Because of its veto power as a permanent member of the council, Britain wields outsized power in world affairs.
British officials held out hope that a show of unity in the Security Council, backed by the threat of an invasion, would force Iraq to back down and agree to full disarmament.
"We're going to go on talking until we find a way forward for the Security Council together," Britain's ambassador to the United Nations, Jeremy Greenstock, told CNN.
Greenstock added, "I'm pretty sure we're talking about action in March. Don't look beyond March."
The new U.N. "benchmarks" would likely require Iraq to allow its weapons scientists to be interviewed outside the country; reveal its stocks of biological and chemical agents or prove that they had been destroyed; and destroy all illegal missiles or other weapons delivery systems, such as drones.
Once those benchmarks were achieved, the United Nations would likely take further time to verify that Iraq had fully disarmed.
Hans Blix, one of the chief U.N. weapons inspectors, is expected to issue a list of key tasks next week that Iraq must perform to satisfy inspectors that it is disarming.
At the United Nations, as of yesterday, American officials were not certain of support from any of the publicly undecided members of the Security Council: Mexico, Chile, Pakistan, Angola, Cameroon and Guinea.
France and Russia, which have each said they would veto any resolution authorizing force, also have been lobbying uncommitted countries to oppose such a resolution.
In a sign of mounting tension as the United States prepares for war, U.N. weapons inspectors temporarily halted U-2 reconnaissance flights over Iraq yesterday after Baghdad complained that a pair of the spy planes were flying, instead of the usual one.
Iraq had sent up fighter jets to intercept the spy planes, according to reports.