WASHINGTON - Democratic and Republican opponents of President Bush's plan to send more troops to Iraq joined forces last night behind the nonbinding resolution with the broadest bipartisan backing - a Republican measure from Sen. John W. Warner of Virginia.

Senate Majority Leader Harry Reid (D., Nev.) announced the shift, hoping to unite a large majority of the Senate and thwart efforts by the White House and GOP leaders to derail any congressional resolution of disapproval of Bush's decision to increase U.S. troop levels in Iraq by 21,500.

Although the original Democratic language was popular within the party, it had little appeal among Republicans. Warner's proposal drew support from both sides, and was retooled last night to maximize both Democratic and Republican votes.

The revised resolution would express the Senate's opposition to the troop buildup but vow to protect funding for U.S. forces. The resolution does not include the Democratic language saying the troop increase is against the national interest, but also drops an earlier provision by Warner suggesting Senate support for some additional troops.

"It's been a hard work in progress," Warner said of the revised resolution, which will require the support of at least 60 senators to prevent a filibuster.

After reviewing the Warner revisions, Reid decided the new text would take the place of the original resolution written by Foreign Relations Committee Chairman Joseph R. Biden Jr. (D., Del.), Armed Services Committee Chairman Carl Levin (D., Mich.), and Sen. Chuck Hagel (R., Neb.). He said that the Senate would begin debating the resolution next week, provided Democrats and Republicans could agree on a way to overcome procedural hurdles.

House Democratic leaders reached the same decision, ordering committees to draft a resolution next week patterned on Warner's language. But House Speaker Nancy Pelosi (D., Calif.) went further, publicly hinting she would push binding legislation that would begin bringing U.S. troops home from Iraq.

"I believe that you'll see initiatives on the floor to this effect: That we have this year in which we should be able to drastically reduce the number of troops," she said in an interview broadcast on National Public Radio. "The Iraqis must build their own country, and we have paid a big enough price."

In both the House and Senate, Democratic leaders decided to get the largest possible vote, even if it meant embracing weaker language than the original Democratic resolution.

White House spokeswoman Dana Perino responded to the announcement, saying: "The president wants to win in Iraq - he's proposed a comprehensive plan to do so, and he's asked Congress to give the plan a chance to work. . . . These resolutions send mixed signals to our troops and our enemy."

Although Bush would not be obliged to follow Congress' direction, should both chambers ultimately pass the Warner resolution, the White House has lobbied hard to prevent such a measure from passing. If the current drive succeeds, it would represent the first formal, bipartisan affront to the administration's Iraq policy since the war began.

Not all Republicans are expected to sign on. Some believe the buildup is a worthy cause that should be given a chance. "The critics stop short of offering any constructive alternatives," said Sen. John Cornyn (R., Texas). "All they have done is just criticize."

Cornyn was assembling his own proposal, which endorses Bush's strategy but calls on Iraq to assume responsibility for security throughout the country by November.

The Warner and Biden resolutions reach almost identical conclusions, in that they oppose the president's additional troop deployment and call for current troops to be reassigned to guard Iraq's borders, combat terrorism, and train Iraqi security forces. Both measures call for regional diplomacy to draw Iraq's neighbors into a peace process.

But Warner revamped his original proposal, both to win over many reluctant Republicans who thought it was too tough and to reassure Democrats who complained he was not being hard enough on the administration.

He added language specifically opposing a cutoff of funding for U.S. troops in a targeted appeal to Sen. Judd Gregg (R., N.H.), who had offered an identical separate measure.