As he prepares to make his case against Iraq to the American people, President Bush is coming under increasing pressure from top congressional Democrats and a few key Republicans to tone down his rhetoric, build greater international support and allow U.N. weapons inspectors more time to work before trying to topple Saddam Hussein.

With polls showing the American public wary of war, Senate Minority Leader Thomas A. Daschle (D-S.D.) said yesterday on CNN that it would be a "terrible tragedy" if Bush launches a preemptive military strike against Iraq without first winning stronger international backing. Sen. Joseph R. Biden Jr. (Del.), the top Democrat on the Foreign Relations Committee, will follow Daschle's remarks with a speech Tuesday urging Bush to allow inspectors additional time to search Iraq for weapons of mass destruction before launching an attack, Democratic officials said.

While most Senate Republicans are voicing their concerns about Bush's posturing in private, Sen. Chuck Hagel (R-Neb.), a respected voice on military matters, warned in a speech at the University of Notre Dame yesterday of "a widening gap between America and the world" over Iraq. "At this precarious juncture in American history, America needs more humility than hubris in the applications of American military power, and the recognition that our interests are best served through alliances and consensus," Hagel said.

In a possible concession to its critics, the White House is considering allowing inspectors another month or so to complete their work before the United States launches a war, administration officials said. In a private briefing for senators Thursday evening, Secretary of State Colin L. Powell and Defense Secretary Donald H. Rumsfeld suggested such a compromise is in the works.

Still the warnings from key lawmakers, which are complicating Bush's campaign to rally support here and abroad for a possible war with Iraq, come at pivotal moment in the showdown with Hussein. U.N. weapons inspectors on Monday are expected to issue a major report on Iraq's compliance with U.N. disarmament mandates.

One day later, in his State of the Union address, Bush will have a prime-time opportunity to amplify his argument that Iraq has refused to cooperate with international weapons inspectors and continues to hide weapons of mass destruction that threaten Iraqi citizens, the United States and its allies. The president in his speech will prepare the nation for the possibility of war to depose Hussein and dismantle Iraq's weapons programs, White House officials said.

In his march toward a possible war, Bush is facing an increasingly skeptical international audience that many lawmakers feel he needs to win over -- or at least pacify -- before proceeding. France, Germany and other traditional U.S. allies are vocally opposing a war in Iraq, while public polls here show Americans worried about the ramifications of going to war without firm, international support.

Republicans and Democrats alike are likely to rally around the president if he strikes Iraq. But with time running out, key lawmakers are trying to pressure Bush to build more international support before taking such military action. These lawmakers contend that broad international support will make it easier not only to win the war but also to rebuild Iraq and keep the peace in the volatile region. At Tuesday's closed-door briefing by Powell and Rumsfeld, several senators urged the administration to give weapons inspectors more time before taking action, participants said.

Afterward, several GOP senators said Bush has to do a better job of explaining why Iraq poses an imminent threat to the United States and how an attack on Iraq fits into his broader war on terrorism. Most Republican lawmakers, however, back Bush's approach and believe the time has come to confront Hussein.

Sen. Carl M. Levin (D-Mich.) lobbied the White House to provide U.N. inspectors more top-secret information about possible weapons sites to aid their search. "So long as there is no imminent threat and so long as Iraq allows weapons inspectors to go where they want, we should listen to the inspectors and what their needs are," Levin said. He said the United States has provided the United Nations only a "small fraction" of its information on weapons sites.

Several Senate Democrats who voted last year to grant Bush virtually unlimited power to strike Iraq are joining Levin in urging Bush to delay war plans.

More than 120 House Democrats, including 23 who voted for the war resolution last year, yesterday sent a letter to the president imploring him to "make every attempt to achieve Iraq's disarmament through diplomatic means and with the full support of our allies." Senate Democrats are circulating a similar letter and seeking signatures of members who voted for the war resolution, but internal disputes over its wording have kept party leaders from making it public, aides said.

Daschle, who voted for the resolution, delivered the most pointed warning to Bush yesterday. "To act precipitously, to act unilaterally, especially in a preemptive manner would be a terrible tragedy and set all the wrong precedents and send the wrong messages to the world community," he said on CNN's "Inside Politics." Several Democrats are expected to voice similar concerns before and after Bush delivers his speech Tuesday.

Still, most Senate Democrats have stopped short of taking the decidedly antiwar position that many liberal activists advocate. Sen. John F. Kerry (D-Mass.) typifies the standard Democratic position -- he believes Hussein represents a grave threat and must be confronted, but only with broad international support.

The Senate plans to give the administration a public forum to outline its concerns with the weapons report Thursday, when the Foreign Relations Committee conducts a hearing to discuss the findings.

Senate Majority Leader Bill Frist (R-Tenn.), right, with Defense Secretary Donald H. Rumsfeld and Secretary of State Colin L. Powell. The secretaries reportedly said a compromise allowing weapons inspectors more time is possible.