President Bush yesterday continued to pick up strong support from the left and right in Congress for a resolution that would give him backing to use military force to disarm Saddam Hussein and possibly remove the Iraqi president from power.

As debate opened in the House and continued in the Senate, many congressional Republicans and Democrats sounded convinced that the United States should strike Hussein -- unilaterally if necessary -- if he does not promptly comply with new and unfettered weapons inspections. "Saddam Hussein will only respond to the credible threat of force or the use of force," said Sen. Evan Bayh (D-Ind.).

In the latest sign that momentum for a strong, bipartisan show of support is building on Capitol Hill, Senate Majority Leader Thomas A. Daschle (S.D.) suggested he plans to vote for the final Bush war resolution. "I am inclined to support it," Daschle told reporters, as an impassioned debate over Iraq raged inside the Senate chamber.

Sen. Tim Johnson (D-S.D.), who voted against going to war with Iraq in 1991, signed up as a co-sponsor of the Bush plan, which gives the president relatively unfettered authority to order an invasion of Iraq. Rep. John Thune (R-S.D.), who is Johnson's opponent in the senatorial election this fall, is running ads linking Johnson to Hussein because he voted against Bush's plan for a national missile defense system.

Republicans said it appears Sen. Lincoln D. Chafee (R.I.) will be the only GOP senator voting against the president. In a speech today, Sen. Chuck Hagel (R-Neb.) will raise concerns that Bush has failed to articulate a plan to rebuild a post-Hussein Iraq, but he is expected to back Bush in the end.

Still, opposition persists on the left. Sen. Robert C. Byrd (D-W. Va.), a master of arcane Senate rules and sharp critic of going to war, may delay a final vote on the resolution until next week by staging a verbal and procedural protest on the Senate floor.

Most congressional opponents of Bush's war resolution favor military action if it is authorized by the United Nations. Senate Armed Services Committee Chairman Carl M. Levin (D-Mich.) is pushing an alternative resolution that would require Bush to come back to Congress for approval to go to war if U.N. efforts fail.

Levin pointed to an assertion by CIA Director George J. Tenet that an attack on Iraq may increase the likelihood Hussein will use weapons of mass destruction as evidence that lawmakers should think twice before giving Bush a green light now.

In a bid to learn more about the threat Hussein poses, Foreign Relations Committee Chairman Joseph R. Biden Jr. (D-Del.) yesterday introduced legislation that would entice Iraqi scientists to defect to the United States by offering a safe haven in exchange for secrets. Biden supports military action in Iraq, but only to enforce U.N. resolutions requiring Hussein to eliminate his dangerous weapons program.

Bush is hoping resounding bipartisan support will prompt the United Nations to adopt a new resolution -- backed by threat of military force -- mandating immediate and unfettered weapons inspections in Iraq.

Secretary of State Colin L. Powell appeared on Capitol Hill yesterday with Republicans and Democrats to challenge the international community to act boldly. The congressional resolution "will definitely strengthen my hand as I try to do the diplomatic work up in New York to get the U.N. Security Council" to act, Powell said.

At a rally yesterday in Knoxville, Tenn., Bush left little doubt that war is a distinct possibility. "The message from Congress, from people from both political parties, will be for the sake of peace. . . . If [the United Nations] won't deal with this man, the United States of America will lead a coalition to disarm him," Bush said.

In a speech Monday, Bush referred to a senior member of al Qaeda who received medical treatment in Iraq. U.S. officials said yesterday that was Abu Musab Zarqawi, a Jordanian, who lost a leg during the U.S. war in Afghanistan. Zarqawi, also known as Ahmad Fadeel al-Khalaylah, first fled to Iran, then Iraq. He has since left Iraq.

On the Senate floor yesterday, Sen. Joseph I. Lieberman (D-Conn.) and Bayh sounded bellicose and dismissive of complaints from some liberals that Bush has failed to prove Hussein poses an imminent threat.

"To those who say, 'What's the rush -- why can't we wait?', I respond by asking the question: How long must we wait?" Bayh said in a speech to the Senate. "Until the missiles have been launched? Until the smallpox, anthrax or VX nerve agent has found its way into our country?"

Lieberman and Bayh were joined by three Democrats facing tough reelection campaigns this year -- Johnson, Mary Landrieu (La.) and Max Baucus (Mont.) -- in co-sponsoring the Bush war resolution in the Senate.

In the House, three days of debate started in the shadow of the Senate. Throughout their first day of debate, lawmakers argued over how much of a threat Hussein posed to the United States and whether the nation could afford to wait before launching military action.

Proponents of the war resolution repeatedly alluded to the policy of appeasement that allowed Adolf Hitler to advance through Europe.

"History has not been kind to governments that have acceded to the wishes of brutal dictators, in the hopes of staving off conflict," said Rules Committee Chairman David Dreier (R-Calif.). Rep. Howard Coble (R-N.C.) was even more explicit. "I do believe Hussein is as brutal, wicked and evil as Adolf Hitler was," he said.

But opponents of the measure said its drafters were presenting the American public with a false choice. "This is not a debate between appeasement and action," said Rep. Diana DeGette (D-Colo.). "It is a question of acting alone versus building a global coalition, as we did 11 years ago, to oppose Iraq's aggression against a peaceful neighbor."

Staff writer Helen Dewar contributed to this report.

Secretary of State Colin L. Powell, second from left, joins Sens. Evan Bayh (D-Ind.), left, Joseph I. Lieberman (D-Conn.) and John W. Warner (R-Va.) at news conference expressing bipartisan support for President Bush on Iraq.