President Bush told Congress yesterday that "the last, best chance for Saddam Hussein to get the message is in your hands" as the House and Senate neared the end of debate on whether to authorize the president to use military force to drive Iraq from Kuwait.

With votes planned today, Bush appeared likely to prevail in the House and began picking up Democratic support in the Senate, where leaders of both parties said they expect him to win at least by a narrow margin.

White House nervousness over prospects in the Senate eased considerably as nine Democrats cosponsored or spoke in favor of the administration-backed resolution authorizing use of force in the Persian Gulf. Several more are believed to be considering voting for the resolution.

Both chambers worked into the early morning as members lined up to speak. The debate is expected to be one of the longest in the House's history.

As an alternative to the White House proposal, Democratic leaders in both chambers are proposing resolutions urging continued reliance on diplomacy and economic sanctions to force Iraq out of Kuwait. But several key Democrats, including Senate Armed Services Committee Chairman Sam Nunn (Ga.), conceded that the alternative is unlikely to be approved.

In speech after speech, lawmakers who support Bush's position argued that an authorization for war offered the best chance of averting conflict because it would persuade Iraqi President Saddam Hussein to leave Kuwait before Tuesday's United Nations-imposed deadline for withdrawal.

With equal passion, those who oppose Bush's policy contended that military force should be held in reserve, sparing lives and potential upheaval throughout the Middle East, until diplomatic and economic pressure is given more of a chance to succeed.

Bush's supporters argued that the passage of a resolution authorizing use of force would not automatically lead to war, while his opponents said it almost assuredly would.

Those aligned with Bush said economic sanctions against Iraq are not working; those lined up against him said they would work if given a chance to do so. Patience is strength, some said; it could become an excuse for inaction, others countered.

With nearly all Republicans lined up behind their president, it was largely an argument among Democrats.

"Our final, best chance for a truly peaceful end to this crisis, I am convinced, is to send a clear and unequivocal message to Saddam Hussein that the American Congress and the American people stand shoulder to shoulder with our president at this critical moment of confrontation," said Sen. Joseph I. Lieberman (D-Conn.) in supporting Bush's position.

"War is not the only option left," argued Sen. Edward M. Kennedy (D-Mass.). "Our policy in the Persian Gulf is not broken, and it cannot be fixed by war. There is still time for the Senate to save the president from himself -- and save thousands of American soldiers . . . from dying in the desert in a war whose cruelty will be exceeded only by the lack of any rational necessity for waging it."

Many lawmakers acknowledged anguish in reaching their decisions and ambivalence even after the decisions were made. In chambers where debates of historic moment are increasingly rare, there were frequent evocations of history and its sometimes contradictory lessons.

"I remember as a young man hearing John F. Kennedy tell this body and the nation . . . that the mere absence of war is not peace," said Sen. Harry Reid (Nev.), the first Democrat to take the Senate floor in support of the president's position. "As long as Iraq continues to occupy and pillage and lay waste to Kuwait, as long as the Iraqi army continues to rape and torture and brutalize and murder the people of that tiny land . . . there is no peace."

Noting the nonviolent revolutions that have swept Eastern Europe and other regions over the past year, Rep. John Lewis (D-Ga.) reached another conclusion. "War is obsolete as a tool and as a means to conduct foreign policy. . . . These people weren't inspired by our bullets and bombs. They were inspired by our Constitution and by our Declaration of Independence," he said.

The significance of the debate appeared to be hitting home across the country. Since it began Thursday, the Capitol switchboard has been swamped. Long delays getting through were reported yesterday. On Thursday, 414,287 calls were handled, nearly twice the usual load.

Passions unleashed by the controversy over war also erupted in the legislative chambers.

As Nunn took the floor to argue against use of force until sanctions are given time to take a toll on Iraq, he was interrupted by protesters in the visitors' gallery who stood up and chanted, "No blood for oil" and "No war for Bush."

When each small group of protesters was dragged out by police, another would stand up and resume the shouting, resulting eventually in an order from the presiding officer to take the rare step of clearing all the public galleries. Eleven demonstrators were arrested and charged with disruption of Congress and demonstrating within a Capitol building.

"For the debate to be interrupted with that kind of outburst simply has no place in the Senate nor in our kind of democracy," Nunn said angrily.

Few of the lawmakers -- even the most ardent presidential supporters -- were willing to embrace the idea of war as such. Instead, they described the power to wage war as a powerful incentive for peace.

"This resolution does not commit President Bush to use military arms, it only gives him that option," said Rep. William S. Broomfield (Mich.), ranking Republican on the Foreign Affairs Committee.

"In the president's hands, it will be a very credible and powerful negotiating tool, particularly at this late hour. . . . We must give the president the power he needs to convince Saddam that he has no other alternative but to leave Kuwait."

"Congressional vacillation makes peace less likely," said Rep. Jim Leach (R-Iowa).

But House Democrats, led by Speaker Thomas S. Foley (Wash.), rejected that argument and said passage of the White House-backed resolution is an invitation to war. Bush has "all but publicly abandoned the hope for diplomacy," Foley said at a news conference, and members would be "wrong to suggest to themselves that they are not voting to give the president the immediate option of going to war. . . . "

"Let us make no mistake about it. The resolution is a declaration of war, a war without announced limits on length or means, a war whose consequences we cannot know and whose costs we cannot calculate," Rep. Mike Synar (D-Okla.) added.

Just as advocates of the war resolution preferred to talk more of peace than armed conflict, many of those who opposed the resolution did not rule out the use of force forever.

"A military offensive to liberate Kuwait may well become necessary, our nation's only option," Sen. Wyche Fowler Jr. (D-Ga.) said. War is justified but "there is a difference between a war being justified or being prudent or necessary. . . ," he added.

"We need to keep the invasion option on the table, right out front where the Iraqis can see it, but I believe it is premature to authorize the president to march on Kuwait," Sen. Lloyd Bentsen (D-Tex.) said.

Some, including Nunn, also questioned how vital Kuwait is to U.S. national security. "We throw around the word 'vital' very carelessly and people in uniform pay the price," Nunn said.

Others, such as Sen. John McCain (R-Ariz.), said the real issue stretches beyond Kuwait. With the power to control the world's oil supplies within Saddam's reach if he is not checked now, McCain said, "We cannot risk putting that capacity in his hands, the capacity of destroying the world's economies."

In a day of low key but intensive lobbying, Bush met with more than 100 House members at breakfast and made calls to wavering lawmakers throughout the day, as did other administration officials, including Defense Secretary Richard B. Cheney and Vice President Quayle.

In the Senate, where most of the lobbying was concentrated, only Mark O. Hatfield (R-Ore.) was considered a certain GOP vote against the president's position, although at least two others are regarded as wavering. But Hatfield said he may also vote against the Democratic alternative, which is expected to provide the key test in the Senate.

Democrats who were publicly supporting the president's position were Sens. Reid, Lieberman, Charles S. Robb (Va.), J. Bennett Johnston (La.), John Breaux (La.), Howell Heflin (Ala.), Richard C. Shelby (Ala.), Richard H. Bryan (Nev.) and Bob Graham (Fla.).

The White House lobbying operation for what could be the most important vote to date drew some criticism yesterday from key aides to Democratic senators who turned against their own leaders in order to support Bush.

One case cited was Sen. Herbert H. Kohl (D-Wis.), who has been known to be sitting on the fence for some time. It was not until yesterday afternoon that Kohl was invited to the White House for a private chat with Bush.

Reid said yesterday that he had not been called by anyone until Bush telephoned him minutes before he was to take the floor to announce his support for Bush's position.

Sen. Alan K. Simpson (R-Wyo.) defended the administration's late start on contacting members of Congress. He said it was not until earlier this week that they had a chance to talk to Democrats and find out who would support the president. "Once the White House started to move, it moved rather quickly," Simpson said.

Staff writers John E. Yang, Dan Balz and Walter Pincus contributed to this report.