President Bush told a televised press conference after a summit among the four nations in the Azores islands, "Tomorrow is the moment of truth for the world."
"Tomorrow is the day that we will determine whether or not diplomacy can work."
Mr. Bush told reporters that the four leaders will spend the coming hours "working the phones, talking to our partners." Asked whether Monday is the final day he will give the United Nations Security Council to craft a diplomatic solution to the Iraq debate, the president responded, "Yes."
The president reiterated the four nations' stance that Iraq remains in breach of United Nations resolution 1441, which called on it to mount a "full and immediate" disarmament campaign.
British Prime Minister Tony Blair called on the international community to "lay down a clear ultimatum" for Iraqi disarmament - a move he said was "entirely within the logic, letter and spirit of resolution 1441."
A British compromise plan presented to international diplomats last week proposed setting disarmament benchmarks for Iraqi leader Saddam Hussein to meet in order to avoid military force. U.N. Security Council members France and Germany, among others, opposed the plan, with French Foreign Minister Dominique de Villepin saying Paris rejected the "logic of ultimatums."
Blair said Sunday that "without a credible ultimatum authorizing force in the event of noncompliance, then more discussion is just more delay, with Saddam Hussein remaining armed with weapons of mass destruction and continuing a brutal murderous regime in Iraq."
"We cannot have a situation where we come back for endless discussion," Blair added.
Should a military conflict arise in Iraq, Blair said the four nations would pledge to help rebuild the country following Saddam's removal and allow the Iraqi people to harness their natural resources - ostensibly including their massive oil reserves - to help stabilize their economy.
"We will protect Iraq's territorial integrity, support representative government that unites Iraq on a democratic basis of human rights," Blair said. "We will do everything we can to minimize the suffering of the Iraqi people."
As the U.S. and its allies prepared a last-ditch effort at diplomacy, the Iraqi leader warned in remarks broadcast Sunday that, if attacked, Iraq would respond in every way it could.
"When an enemy starts a large-scale battle, he must realize that the battle between us will be open wherever there is sky, land and water in the entire world," he told a meeting of military commanders.
Saddam said allegations that Iraq still possessed banned weapons were a "great lie," adding, "I don't believe the world has seen this level of lying ...as that coming out from America and Britain."
Earlier Sunday, diplomatic wrangling over Iraq continued, with French President Jacques Chirac telling a reporter from CBS's 60 Minutes that he was willing to accept a 30-day deadline for Iraqi disarmament, as long as the move was endorsed by the lead U.N. weapons inspectors.
"One month, two months, I am ready to accept any accord on this point that has the approval of the inspectors," Chirac said, according to excepts released by his office.
France has remained one of the most vocal opponents of a U.S.-backed resolution authorizing war in Iraq if Baghdad does not disarm. Chirac said last week France would use its veto power to scuttle a resolution authorizing war in Iraq.
Vice President Dick Cheney rejected the proposal, telling NBC's Meet the Press that it was "difficult to take the French serious and believe that this is anything other than just further delaying tactics."
Referring to the French opposition during his remarks in the Azores, President Bush said that by promising a veto, French leaders "have showed their cards," adding, "We'll have to tell you tomorrow what that card meant."