WASHINGTON — Republicans and Democrats can each claim their own veterans in the fight over legislation that would mandate that soldiers serving in Iraq would get to return home for the same amount of time they spent in Iraq.

The amendment, authored by Senator Webb, a Republican from Virginia, attracted votes from seven Republicans but lost on procedural grounds on the Senate floor. The Democratic leadership has touted the legislation as “pro-military,” calling a press conference yesterday featuring National Military Families Association, Vote-Vets.org and Veterans for America, formerly the main association for veterans of the Vietnam War. Yesterday, however, spokesmen for the American Legion, Veterans of Foreign Wars, AMVETS, and Catholic War Veterans of the USA all said that their organizations would not endorse Mr. Webb’s amendment. They said the senator had not sought their endorsements.

The Webb amendment has been criticized by the Senate minority leader, Mitch McConnell, a Republican from Kentucky, for making it next to impossible to reinforce the current troop surge in Iraq. On the floor of the Senate this week, Mr. Webb, a former Marine who served as secretary of the Navy in the Reagan administration, read a letter of endorsement from the Military Officers Association of America. It said in part that the organization was concerned that “steps must be taken to protect the most precious military asset, all volunteer force, for having to bear such a disproportionate share of wartime sacrifice.”

Mr. Webb’s amendment, as well as others from Democrats such as Senator Levin of Michigan to set a firm deadline next year for the withdrawal of most troops from Iraq, have concerned the White House. The national security adviser, Stephen Hadley, was dispatched to meet with senators to persuade them to hold off of casting votes to end the war until the commanding American general in Iraq, David Petraeus, delivers his reports to Congress in September.

A spokesman for the Veterans of Foreign Wars, Joseph Davis, yesterday said he supported the concept of giving volunteer soldiers a minimum of home deployment. But he added, “The big question is how do you enforce this during a time of war? What happens if another balloon goes up elsewhere? How do you send troops if they haven’t got their required rest time?”

A spokeswoman for the American Legion, Ramona Joyce, said Mr. Webb had not sought the opinion of the American Legion on his amendment. Ms. Joyce said deployment policy is “best left up to the commanders and the executive branch . . .The ground commanders and the Executive Branch are the ones who run the war. There aren’t any generals in Congress that I’m aware of.”

A spokesman for AMVETS, Joe Chenelly, said yesterday that his organization did not have a formal position on the Webb amendment. “We have been looking at that very carefully, and we haven’t heard enough of a response from both parties to have a concrete stance yet, but we do caution, and in most cases are against, hamstringing commanders, and this is what this looks like.”

Seven Republicans voted for the Webb amendment yesterday, including Senator Hagel of Nebraska, Senators Snowe and Collins of Maine, Senator Smith of Oregon, Senator Sununu of New Hampshire, Senator Warner of from Virginia, and Senator Coleman of Minnesota. In the end a motion to end debate in the Senate on the amendment passed by 56 to 41, not enough votes to stave off a filibuster.

Senator Coleman, who also supported an amendment by Senator Lieberman, an independent Democrat from Connecticut, instructing the Pentagon to provide regular reports on Iran’s role in aiding the insurgency, had wavered in January on his support for the war but ended up voting with Republicans against amendments calling for deadlines for withdrawal.

Yesterday, Mr. Coleman, who is up for re-election to his seat in 2008, said, “The number one concern I heard from those husbands and wives, moms and dads, and sons and daughters, was that their loved ones might only be home for a short time before deploying to Iraq again. To me, this vote wasn’t about our policies in Iraq. It was about our troops. I believe we owe them as much time at home between deployments as we possibly can, and that is why I supported the Webb Amendment.”

The Senate majority leader, Harold Reid, a Democrat of Nevada, criticized Republicans who voted against the Webb and Levin amendments. “Republicans had two opportunities today to match their words with action and support the soldiers who are risking their lives in Iraq and bearing the burden of this open-ended civil war,” he said. “But they instead demonstrated that they do not care about rebuilding our badly overextended military, nor about ensuring our troops have the time to properly train, prepare for and recover from battle.”

Democrats are expected to offer versions of Mr. Webb’s amendment in the future in their bid to end the war. Meanwhile, one of the points they will sound in the debate is that the Iraq war has wrecked the military. In Iraq, General Petraeus said this week that 588 troops reenlisted in an event over July 4. A spokesman for the general, Colonel Steven Boylan, said, “On troop morale, for the most part what we see is fine. It goes up and it goes down based on the events of the day.”