Addressing the Speaking Council just hours before the end of Bush's 48-hour ultimatum, Russian Foreign Minister Igor Ivanov said his country would help the war effort, "if today, we really had indisputable facts demonstrating that from the territory of Iraq there was a direct threat to the United States."
But no proof had been produced, Ivanov said, and the authority of the United Nations had been superceded.
Despite the lack of U.N. approval and widespread opposition to the war in the Muslim world, the Bush administration has maintained that there was an international "coalition of the willing" backing a war. Earlier this week, Secretary of State Colin Powell released a list of 30 nations that had joined that group.
International opposition to the war in recent months has centered around doubts about the Bush administration's rationale for launching "pre-emptive strikes" against Iraq.
In November 2002, U.N. weapons inspectors returned to Iraq after a four-year absence, when the Security Council unanimously voted Resolution 1441 granting Iraq a "final opportunity to comply with its disarmament obligations."
But Washington's efforts to get a new resolution authorizing the use of military force passed by the Security Council proved to be an uphill diplomatic challenge, with France threatening to veto any new resolution.
The diplomatic effort was eventually abandoned on Monday, when Britain's U.N. ambassador, Jeremy Greenstock, announced that Britain and the United States would not submit a new U.N. proposal.
But even as a war of words raged in the corridors of the United Nations, the Pentagon had begun a massive military buildup in the region in recent months.
An estimated 300,000 troops, including British military personnel, backed by more than 1,000 warplanes, were placed in the region, for an attack before today's call to war. The troop buildup has been commandeered from a command center headquartered in Qatar.
The Bush administration has maintained that the Sept. 11, 2001, attacks on the United States had highlighted the potential threat to national and international security from individuals and nations amassing weapons of mass destruction.
But critics — including governments of countries on the Security Council — have questioned Washington's allegations that Saddam has links to the al Qaeda terror network, which the United States holds responsible for the Sept. 11 attacks.
And the Iraqi government has repeatedly maintained that it does not possess banned weapons of mass destruction, a claim Washington and London rejects.
On Monday, in a speech that marked the culmination of the rupture between America and the United Nations, Bush condemned the international organization's failure to sanction a war with Iraq.
"The United Nations Security Council has not lived up to its responsibilities," Bush said. "So we will rise to ours."
Bush however gave the Iraqi president two days to flee or face the might of the U.S. military.
It was an ultimatum that Saddam rejected the very next day after a rare television appearance on Iraqi state television. In a statement broadcast across the nation, the Iraqi Cabinet said, "Iraq and all its sons were fully ready to confront the invading aggressors and repel them."
ABC News' Michael S. James and Bryan Robinson contributed to this report.