President Bush won significant support yesterday for invading Iraq from key members of Congress but failed to mollify the vocal minority of lawmakers opposed to deposing Saddam Hussein without broader international backing.

With war looking imminent and unavoidable, most congressional Republicans and Democrats began rallying around their commander in chief and countering criticism here and abroad that Bush is rushing into war in defiance of the United Nations.

"The president has shown great patience and given diplomacy every chance to work," said Senate Majority Leader Bill Frist (R-Tenn.). "The stark choice presented to Saddam's regime is fully justified: Leave or be removed."

Even the harshest of war critics in Congress expressed unequivocal support for the 250,000-plus troops stationed around Iraq awaiting the president's call to invade. Many vowed to tone down their opposition to military action soon in deference to those in uniform.

Still, key Senate Democrats picked up where France and other international critics left off, blasting Bush for failing to work harder to win over world leaders wary of war and to tamp down the anti-American fervor sweeping much of Europe and the Middle East before proceeding.

"I'm saddened that the president failed so miserably at diplomacy that we are now forced into war," Senate Minority Leader Thomas A. Daschle (D-S.D.) told union workers yesterday.

Four hours later, Daschle joined top lawmakers for a private Iraq briefing at the White House hosted by Bush and Vice President Cheney.

Once the bombs start dropping, many congressional critics may fall largely silent. After hitting Bush for his "failed diplomatic efforts," Sen. Frank Lautenberg (N.J.), echoing many of his Democratic colleagues, said, "As a veteran, I know what it means to have the strong support of Americans back home."

In the short term, at least, Congress will focus much of its war-related energies on devising means to pay for the conflict while considering the cost and logistics of rebuilding Iraq in the aftermath. Bush did not provide lawmakers with a cost estimate yesterday, said those who met with him.

Most lawmakers, including Daschle, voted five months ago to authorize Bush to wage war without the United Nations' permission; few have changed their minds since. That was the last time Congress voted on the wisdom of the impending war. Symbolic resolutions supporting Bush and the war effort are expected to pass the House and Senate soon after an attack is launched.

Bush enjoys near-universal support among congressional Republicans for attacking Iraq when he chooses, although several of them privately raised concerns about his tactics and timing. Bush "has strong support in Congress . . . and we will do whatever we can to support the president when he comes to ask for any funding he may need," said Sen. Rick Santorum (R-Pa.).

Democrats remain split into three camps: those who support war, those who oppose it and those who want a U.N.-sanctioned encounter. Presidential contenders such as Sen. Joseph I. Lieberman (Conn.) and Rep. Richard A. Gephardt (Mo.) are leading the party's pro-war forces -- an unpopular position among many rank-and-file Democratic activists.

Sen. Joseph R. Biden Jr. (Del.), the ranking Democrat on the Foreign Relations Committee, is among the most prominent of the many Democrats who see Hussein as a deadly threat best eliminated with a coalition similar to the one assembled for the Persian Gulf War.

The antiwar faction, small but vocal, is led by Sens. Edward M. Kennedy (Mass.) and Robert C. Byrd (W.Va.). "I think many of us in Congress are disappointed that weapons inspectors are not being given adequate time to work," Kennedy said yesterday. "As long as weapons inspectors on the ground are making progress, I believe we should not pull the trigger on war."

The most ardent of antiwar Democrats showed no signs of retreat. The lawyer representing a few of these members yesterday announced he was resubmitting a lawsuit to thwart U.S. military action, contending that only Congress has the constitutional right to declare war. The courts have rejected similar cases twice this year.

"I am going to continue to speak out and challenge this administration's policies that are putting this nation at greater risk," said Rep. Dennis J. Kucinich (Ohio), who is running for president as an antiwar candidate. "This war must be challenged. It's wrong. It will ruin this country."

The debate over Iraq is expected to dominate this week's negotiations over the 2004 federal budget. GOP congressional leaders are planning swift action on budget resolutions including the first wartime tax cuts in history, though a rebellion by moderates in their own party threatens to curtail or derail their most ambitious plans.

Sen. John McCain (Ariz.) is among several Republicans calling for the tax cut debate to pause until the war costs are tallied in the months ahead. As important, a small group of moderates in the House and Senate are demanding a tax cut half the size of Bush's or smaller.

Bush is expected to ask Congress next week for $75 billion or more to wage the war and rebuild Iraq afterward -- in addition to funds already appropriated and spent on the military buildup. At some point, Congress also will be asked to approve new war-related aid packages to U.S. allies such as Israel and Jordan to compensate the countries for economic disruptions resulting from the conflict. With deficits projected to hit record levels in dollar terms, the spending requests will only complicate passage of the Bush tax plan, lawmakers said.

Staff writer Dan Morgan contributed to this report.

Sen. Robert C. Byrd (W.Va.), a leader of the antiwar Democrats, left, joins Sen. John W. Warner (R-Va.) after a White House briefing on Iraq. Sen. Joseph R. Biden Jr. (Del.) is among a group of Democrats who support the war but would like to have a stronger coalition.