From left, US Senators Hagel, Biden and Levin

The non-binding measure expresses opposition to President Bush's decision, announced last week, to send another 21,500 troops to Iraq.

It is sponsored by the Democratic chairman of the Senate Armed Services Committee, Senator Carl Levin of Michigan, the Democratic chairman of the Senate Foreign Relations Committee, Senator Joe Biden of Delaware, and Republican Senator Chuck Hagel of Nebraska, a long-time critic of the president's Iraq policy. "I will do everything I can to stop the president's policy as he outlined it on Wednesday night. I think it is dangerously irresponsible. To continue to put American lives in the middle of a clearly defined, tribal, sectarian civil war is wrong," he said.

The resolution is aimed at forcing Republicans to take a stand on President Bush's handling of the war, which is unpopular with the American people.

Senator Biden, who, like Hagel, is considering running for president in 2008, says the resolution is aimed at pressuring Mr. Bush to change course in Iraq. "The more we -- we on a bipartisan basis -- showed the American people across the board that we do not want to go down this path of escalation the better our chances to get him to reconsider his approach," he said.

Biden says his Foreign Relations Committee will send the resolution to the Senate floor next week, after the President Bush's State of the Union address Tuesday night.

The House of Representatives is to consider simmilar meassures later this month.

Senator Hillary Clinton, a New York Democrat who is another likely contender for her party's nomination for president in 2008, says she, too, opposes a troop increase in Iraq and is proposing a cap on the number of U.S. soldiers there to the current 130-thousand.

Clinton, who just returned from a fact-finding trip to Iraq, said the United States should cut funds for the training and equipping of the Iraqi military if the country's Shi'ite leaders fail to give minority Sunnis a greater role in government. "I do not support cutting funding for American troops, but I do support cutting funding for Iraqi forces if the Iraqi government does not meet set conditions," she said.

At the White House, spokesman Tony Snow was critical of the Clinton proposal to cap the number of troops. "It binds the hands of the commander in chief and also the generals and frankly also the troops on the ground in terms of responding to situations and contingencies that may occur there. To tie one's hands in the time of war is a pretty extreme move," he said.

The White House does appear concerned about eroding congressional support for its Iraq strategy. President Bush and his national security adviser Stephen Hadley invited skeptical Republicans to the White House for private meetings about Iraq.

The White House received a blow last week, when one of its staunch allies, Republican Senator Sam Brownback of Kansas, announced his opposition to a U.S. troop increase. Brownback, who visited Iraq recently, repeated his comments on the Senate floor Wednesday. "Sunni leaders blame everything on the Shi'ia, and the Shi'ia leaders likewise blame everything on the Sunnis. Kurdish leadership pointed out that the Sunnis and Shi'ia only meet when the Kurds call a meeting. All of this suggests that at the present time, the United States seems to care more for a peaceful Iraq than the Iraqis do. If that is the case, it is difficult to understand why more U.S. troops would make a difference," he said.

Still, the Bush administration does have its supporters. Senator Kit Bond, a Missouri Republican, is among them. "I happen to believe it is the best available option to support the Iraqis who have committed to end the insurgency, to bring in the Sunnis into a government that would share in the oil revenues, and take responsibilities for ending the insurgency while our troops go after the external forces, the terrorists coming in from other countries joining the al-Qaida movement," he said.

Some Republican backers of the president's Iraq plan are considering introducing their own resolution expressing support for the strategy.