House Democratic leaders announced their proposal for the $100 billion-plus Iraq War spending bill Thursday morning, including a timeline that could lead to the redeployment of U.S. troops as early as this summer and no later than next. But it remains to be seen whether the measure will satisfy rank-and-file Democrats and bridge fissures within the majority that had slowed the bill’s development.

In addition to a withdrawal timeline, other key elements in the measure include enforcement of guidelines for training of military personnel, mandatory rest periods between deployments and limitations on extending tours of duty, as well as shifting attention to Afghanistan and additional funds for veterans’ health care.

The proposal outlined by Speaker Nancy Pelosi (D-Calif.) and other senior Democrats would require the White House to issue a series of status reports certifying whether the Iraqi government has met “certain political benchmarks” and would directly tie plans for redeployment to those accounts.

“No matter what, by March 2008, redeployment begins,” Pelosi said. The measure would make an exception for military personnel to train Iraqi forces and also for those assigned to protect diplomatic facilities.

As expected, the White House said Thursday that President Bush likely would veto such a bill if it reached his desk.

“Obviously, the administration would vehemently oppose and ultimately veto any legislation that looks like what was described today,” Bush aide Dan Bartlett said on Air Force One, according to Agence France-Press.

According to Pelosi, the bill would mandate that Bush submit his first benchmark status report in July. Those standards to which the Iraqis would be held would be drawn from a January announcement made by Bush, in which he outlined the administration’s latest war strategy.

Failure to show progress on those benchmarks by July would prompt the immediate implementation of a 180-day withdrawal plan, Pelosi explained.

A positive report, however, would result in Iraq receiving an extension to October 2008 to complete those goals, at which time the president would be required to submit a second status report. A failing report at that time would prompt the execution of the 180-day withdrawal plan, while a positive update would permit U.S. troops to remain in Iraq until March 2008, and only then would the withdrawal plan take effect.

“If everything goes as well as possible … then even in that case our troops must be out of a combat role by August 2008,” Appropriations Chairman David Obey (D-Wis.) said at the Thursday morning press conference.

But it remains to be seen whether that withdrawal proposal will satisfy the 70-plus members of the Progressive Caucus who introduced an amendment Thursday morning that would require withdrawal of the U.S. military before the end of the current year.

“We are a Caucus and we will come together and find our common ground,” Pelosi asserted.

Under an amendment authored by Rep. Barbara Lee (D-Calif.), any funds provided by the supplemental could be used only for an organized withdrawal, including the protection of both troops and contractors, although diplomatic and reconstruction work would be allowed to continue.

“We want a plan that will fund a safe and secure exit of our troops from Iraq in a reasonable time,” said Rep. Maxine Waters (D-Calif.), a member of the Progressive Caucus. The California lawmaker added that the group expected Democratic leaders to offer them language addressing their concerns following a Wednesday night meeting.

But Pelosi, who said leaders have not determined if amendments will be allowed to the spending bill, suggested the lawmakers would not be receiving any specific provisions. Instead: “They may want some clarification in the language.”

In the meantime, however, members of the Progressive Caucus indicated they could oppose any measure that allows the president to waive guidelines dictating training levels for military personnel, mandatory rest periods between deployments and limitations on extending tours of duty.

“We don’t support any plan that would give this president the opportunity to waive” those requirements, Waters said

While Democrats have steadfastly maintained they would not reduce funds to military personnel, the measure would reduce by 10 percent, or about $815 million, funds paid to non-government contractors currently providing services to troops deployed in both Iraq and Afghanistan.

Rep. John Murtha (D-Pa.), chairman of the Appropriations subcommittee on Defense, said contractors will be required to validate their current spending levels to Congress, and those funds could be restored after those reports have been received.

“I’m convinced they won’t be able to justify it,” Murtha said.

The measure is expected to be marked up by the full Appropriations panel next week and will move to the House floor the following week.

Minority Leader John Boehner (R-Ohio) said he would vote against the supplemental and expected almost unified opposition from Congressional Republicans. “We are not going to vote for failure in Iraq,” he said.

Boehner attended a video-conference at the Pentagon this morning with Army Gen. David Petraeus, the top U.S. commander in Iraq, and knocked Democrats for not attending.

“There was not a single member of the Democratic leadership in the House there this morning despite being invited,” he said, “I think it’s unfortunate but telling. … Gen. Petraeus should be the one making decisions about what happens on the ground in Iraq, not Nancy Pelosi or John Murtha.”

While Pelosi declined to offer specifics on how many Republicans could be expected to support the final version of the spending bill — stating only that she hopes for support — she bucked suggestions that the measure would be altered by the threat of a potential veto.

“You never confine your best work, your hopes your dreams, the aspirations of the American people, to what will be signed by George W. Bush because that is too limiting a factor,” Pelosi said.

Susan Davis contributed to this report.