WASHINGTON - Two senators leading separate efforts to put Congress on record against President Bush's troop buildup in Iraq joined forces yesterday, agreeing on a nonbinding resolution that would criticize the plan.

Sens. John W. Warner (R., Va.) and Carl Levin (D., Mich.) had been sponsoring competing measures opposing Bush's strategy of sending 21,500 more U.S. troops to the war zone, with Warner's less harshly worded version attracting more Republican interest. The new resolution would vow to protect funding for troops while keeping Warner's original language expressing the Senate's opposition to sending additional forces.

The resolution could well gain more support from members of both parties than Levin's and Warner's separate versions had been attracting. It lacks Levin's language saying the troop increase is against the national interest, and it drops an earlier provision by Warner suggesting Senate support for some additional troops.

It also is likely to pose a threat to the White House because of its potential appeal to Republicans who have grown tired of the nearly four-year war and want a chance to express their concerns. The White House has been hoping to avoid an overwhelming congressional vote criticizing Bush's handling of the war.

"It's been a hard work in progress," Warner said of his resolution, which has been struggling to win the support of 60 senators, a sufficient number to thwart a filibuster.

The agreement came as several leading Republicans who support the troop buildup said they would give the administration and the Iraqis about six months to show significant improvement. Many other Republicans say they are deeply skeptical that additional troops in Iraq, rather than a political settlement, would help calm the sectarian violence.

The widely unpopular war has led to the deaths of more than 3,000 U.S. troops, and is blamed for GOP losses in the Nov. 7 elections that handed control of Congress to the Democrats.

Senate debate on the new resolution, and several proposed by other senators, is likely to begin next week.

The House previously had planned on waiting for the Senate to vote first as a way of testing the waters for Republican support of such a resolution. But according to a Democratic aide, the House will begin the process next week with a committee review. That would set the stage for a House floor debate the week of Feb. 12.

Warner, a prominent Republican and former chairman of the Armed Services Committee, had attracted at least seven other Republicans who were inclined to vote for his resolution. Scrambling to find additional support, he added language proposed by Sen. Judd Gregg (R., N.H.) that would protect funding for troops.

As of late yesterday, Gregg had not said whether he would support the revised resolution.

"Colleagues have come up to me and said: 'Can you assure me that this doesn't provide a cutoff of funds?' " Warner said.