House Republicans defeated a preliminary measure that would have required troops to begin withdrawing from Iraq within 90 days, but a vote on a broader war funding measure was still set for later Thursday.

The measure that was defeated was a bill sponsored by Rep. Jim McGovern, D-Mass., a member of the "Out of Iraq" caucus of progressive Democrats. The bill called for pulling out U.S. troops within 90 days and completing the withdrawal within six months. The measure failed by a heavily partisan vote of 255-171.

The broader piece of legislation still awaiting a vote would provide the military $42.8 billion to keep operations going for two-and-a-half more months, buy new equipment and train Iraqi and Afghan security forces. Congress would decide shortly before its August recess whether to release an additional $52.8 billion to fund the war through September.

The House bill faces Republican opposition and lacks support in the Senate.

Earlier in the day President Bush pulled no punches in warning congressional Democrats that failure to give U.S. troops in Iraq the resources they need to battle a rising Al Qaeda threat will lead to disaster.

"We should be able to agree that the consequences of failure in Iraq would be disastrous for our country," Bush said at the Pentagon after meeting with Defense Secretary Robert Gates and other military officials. "We should be able to agree that we have a responsibility to provide our men and women on the front lines the resources and flexibility they need to do the job we asked them to do."

Bush renewed his threat to veto the House war spending bill.

"I'll veto the bill if it's this haphazard piece-meal funding," Bush said after the White House acknowledged Republican concerns that the war could damage the party's political future.

"My message to the members of Congress is: Whatever your beliefs may be, let's make sure our troops get funded. And let's make sure politicians don't tell our commanders how to conduct operations, don't hamstring our people in the field," Bush said.

The House bill faces Republican opposition and lacks support in the Senate.

But Democrats continued to move on the legislation after vowing to challenge Bush on the war and to stay on message and not give the president a blank check to fund military operations.

"The president refuses to listen to the American people who want this war to end," said House Speaker Nancy Pelosi, D-Calif.

On the House floor Thursday Rep. Jack Murtha, D-Pa., said a visit by Republicans to the White House on Wednesday appeared to have prompted some changes in the president's stance.

"I'm glad to see some Republicans went to the White House and spoke the truth to this president and said to him, 'Mr. President, we need a change, you're destroying the Republican Party," Murtha said.

"I see in a news release that the president is now after all this time considering benchmarks. ... He's come off the pedastal. And the president's starting to begin to realize that something has to be done to change the direction of this country," Murtha said.

On the Senate side, Senate Majority Leader Harry Reid told reporters he sees a change in the Bush administration.

"It's very clear that the people around the president recognize there are some problems," said Reid, D-Nev. "And I think I have felt with my conversations with administration officials that there is a right admission that things are not going very well."

Senate Democrats said they anticipate a vote on a war bill by next week, although Reid said it remains unclear what the Senate bill might look like.

Bush also indicated his support for setting benchmarks for the Iraqi government.

"One message I have heard from people of both parties is that benchmarks make sense and I agree," Bush said.

Earlier this week, nearly a dozen moderate House Republicans went to the White House to tell Bush in no uncertain terms that the war in Iraq was unsustainable without public support and was having a corrosive effect on GOP political fortunes, lawmakers disclosed Wednesday.

White House spokesman Tony Snow acknowledged the meeting.

"It is striking to me ... that people are shocked that the president is hearing candid advice from people who have concerns," Snow said Thursday during a briefing with reporters.

"And I'm telling you that where the rubber meets the road, right now here in Washington, Republicans are united, Democrats are divided. Period." Snow said. "If you want disunity, there's far more disunity on the Democratic side."

The discussion, described by the 11 participating lawmakers as blunt, preceded the president's threat Wednesday to veto the House bill now under consideration.

Gates sent Congress a letter Thursday urging lawmakers to pass an emergency supplemental bill immediately.

“The lack of timely supplemental funds has limited the department’s ability to properly contract for the reconstitution of equipment for both active and reserve forces,” Gates wrote in the letter.

Gates wrote that the proposal to fund operations only through July “would cause significant disruption to the effective and efficient operation of the Department of Defense and the health and welfare of the U.S. military."

Rep. Charles Dent of Pennsylvania said he told the president that many of his constituents are "impatient, and in some cases have a sense of futility" about the war.

Rep. Tom Davis of Virginia said he presented recent polling data from his suburban Washington district showing Bush's unfavorability ratings exceeded his approval ratings.

"We asked them what's Plan B. We let them know that the status quo is not acceptable," he said. Davis said the president responded that if he began discussing a new strategy, the current one would never have a chance to succeed.

In Iraq, Vice President Dick Cheney vowed to "stay on the offensive" during a visit with U.S. troops stationed near former Iraqi leader Saddam Hussein's hometown.

"Many of you have had your deployments extended and that puts unexpected hardship on you and your families. I want you to know the extension is vital to the mission," Cheney said.

Meanwhile, senior Iraqi government officials met with lawmakers on Capitol Hill this week. Some lawmakers said they seemed to want more time to show progress.

Iraqi Deputy Prime Minister Barham Saleh met with Reid and Sens. Richard Lugar, R-Ind., and Norm Coleman, R-Minn., FOX News has learned.

Lugar said a number of members brought up the highly-controversial two-month recess the Iraqi Parliament has scheduled for the summer.

FOX News' Molly Hooper, Trish Turner and The Associated Press contributed to this report.