The compromise - the product of negotiations by the White House and bipartisan House and Senate leaders - won broad backing. It would allow Bush to invade Iraq, provided he declared to Congress that further diplomacy was useless and that an attack would not hinder the war on terrorism.
Leaders on both sides of the Capitol predicted that the proposal would win congressional approval.
"The statement of support from the Congress will show to friend and enemy alike the resolve of the United States," Bush said yesterday, flanked by Republicans and Democrats in the White House Rose Garden.
"Saddam [Hussein] must disarm, period. If he persists in his defiance, the use of force may become unavoidable," the president said of the Iraqi leader.
Emboldened by the rising support in Congress, the administration is also preparing to take a harder line with other permanent members of the United Nations Security Council in pushing for a new U.N. resolution against Iraq.
After a month of contentious debate on Capitol Hill about U.S. policy on Iraq, including wrangling over the language for a congressional resolution, House Democratic leaders and rank-and-file members of both parties fell in line behind the president's position.
"Iraq's use and continuing development of weapons of mass destruction, combined with efforts of terrorists to acquire such weapons, pose a unique and dangerous threat to our national security," said Democratic Rep. Richard A. Gephardt, the minority leader in the Republican-led House, who stood beside Bush. "We need to deal with this threat diplomatically if we can, militarily if we must."
Some senators, including Majority Leader Tom Daschle, a South Dakota Democrat, said they remain opposed to such a broad grant of authority for Bush to wage war. But they conceded that they had little chance - given the backing of House Democratic leaders - to prevail with an alternative measure.
"The honest answer is, it's probably too late," said Sen. Joseph R. Biden Jr., the Delaware Democrat who is chairman of the Foreign Relations Committee.
Biden has been pushing a more limited resolution, along with the ranking Republican on his committee, Sen. Richard G. Lugar of Indiana. But he predicted that the House would pass the Bush compromise by a wide margin. And he seemed to concede that the Senate would follow suit.
"I'm a realist," Biden said.
Daschle conceded that the measure agreed to yesterday includes "improvements" that White House negotiators have made during the past two weeks. But Daschle and a group of Senate Democrats and Republicans seek further changes.
"The final resolution should include greater emphasis on eliminating Iraq's weapons of mass destruction, a stronger statement that operations against Iraq will not undermine the ongoing international effort against al-Qaida, and a clearer assessment of the administration's plan for the political and economic reconstruction of a post-Saddam Iraq," Daschle said in a statement.
The Senate is expected today to begin floor debate on Iraq, while the House International Relations Committee works on the compromise measure.
A small group of protesters was escorted from the International Relations Committee room yesterday after interrupting the session with shouts of "Americans do not want this war!" and "We ask you please to not go to war - the American people don't want it!"
Some House Democrats are likely to try to alter the resolution today through amendments. But Rep. Henry J. Hyde, the Illinois Republican who is chairman of the International Relations Committee, said he would try to preserve the White House language.
Biden and Lugar want a chance for a vote on their proposal, which Daschle has endorsed. They are seeking to narrow the president's authorization so that force could be used only to protect U.S. security or to disarm Saddam Hussein.
By contrast, the compromise agreed to yesterday would allow force to be used to defend the nation or to enforce "all relevant" U.N. Security Council resolutions on Iraq. That language, Biden argues, could empower the president to go to war for other reasons, such as forcing Hussein to cease human rights abuses against Iraqi citizens or to free non-Iraqi prisoners.
Administration officials said Bush has no intention of using force for such reasons.
The Biden-Lugar resolution would also require Bush to either delay the use of force until the United Nations has approved a new resolution intended to disarm Hussein, or certify that the Iraq threat is "so grave that the use of force is necessary" even without international support.
Sen. Carl Levin, the Michigan Democrat who chairs the Senate Armed Services Committee, is drafting a resolution to go a step further in limiting Bush's authority. It would allow the president to use force - but only after the United Nations had adopted a resolution calling for unfettered weapons inspections, disarmament of Iraq and the use of force by member nations if those requirements were not met.
A vocal minority of Democrats, including Sens. Barbara A. Mikulski and Paul S. Sarbanes of Maryland, have expressed wariness about a U.S. invasion conducted without the backing of U.S. allies
Lieberman said now is "the hour for members of Congress to draw together across party lines to support the national security of the United States."
McCain said it would be "unwise" to try to limit Bush's authority when Congress agrees with him that Iraq poses a threat to the United States.
The measure garnered the support of Gephardt and several other Democrats in part because it included changes they had sought requiring Bush to justify military action.
The president would have to declare to Congress within 48 hours of using force that further diplomacy "will not adequately protect the national security of the United States," or would be unlikely to secure the enforcement of U.N. resolutions.
Bush would also have to certify that an invasion of Iraq would not interfere with the war on terrorism. Also, he would have to report to Congress every 60 days during the conflict.
At the United Nations, U.S. officials pushed for a resolution spelling out tough terms for weapons inspections and threatening "all necessary means" - a euphemism for military action - if Iraq balked.
Russia showed signs of moving closer to the U.S. position, with Foreign Minister Igor Ivanov saying, "If any extra resolutions are required for the effective work of the inspectors, we, of course, are ready to consider them."
Sun staff writer Mark Matthews contributed to this article.