Two Democratic lawmakers plan to introduce legislation when the Senate returns from its spring recess next week that would effectively cut off funding for the troops in Iraq and require them to be redeployed from that country by March 31, 2008.

The legislation by Majority Leader Harry Reid and Wisconsin Sen. Russ Feingold is the "next step" in the Iraq debate, a spokesman for Feingold told FOX News on Monday. The new legislation essentially gives a hard deadline to language passed by the Senate last week in a supplemental war spending bill.

The supplemental war spending bill listed March 31, 2008, as a suggested goal for withdrawing all U.S. combat troops from Iraq. The new legislation would reinforce that date by preventing funding for the mission after that deadline.

"No funds appropriated or otherwise made available under any provision of law may be obligated or expended to continue the deployment in Iraq of members of the United States Armed Forces after March 31, 2008," reads the measure.

Like the earlier bill, which passed 50-48 in the Senate, the Feingold measure also requires the president to begin redeploying U.S. troops from Iraq 120 days from enactment. It makes exceptions for funds designated for targeted operations against Al Qaeda and other terrorist groups; security for U.S. infrastructure and personnel; and training and equipping of Iraqi security services.

“Congress has a responsibility to end a war that is opposed by the American people and is undermining our national security. By ending funding for the president’s failed Iraq policy, our bill requires the president to safely redeploy our troops from Iraq," Feingold said in a written statement.

The earlier spending bill must first be reconciled with a House version that calls for redeployment by September 2008. President Bush has said he would veto any spending bill that has a declared timetable for withdrawal. He also criticized the bill for piling on billions of dollars in special home state projects.

At the White House, spokeswoman Dana Perino said she doesn't know what polling led Reid to change his mind about "standing with the troops."

"Well, there's just these shifting sands when it comes to the Democrats and their decisions," she said. "It's almost shifting so fast, it's like a sandstorm."

Reid said if the president does veto the supplemental bill, he "will work to ensure this legislation receives a vote in the Senate in the next work period.”

More Than One Reason for Veto

On Monday, House Minority Leader John Boehner released a letter to the president signed by 154 Republicans vowing to sustain his veto of any war supplemental spending bill that contains pork-barrel spending Democrats added to secure its passage.

The letter is a by-product of the closed-door meeting Bush had with House Republicans last week. Boehner had been lobbying the White House to oppose the Democrats' war-funding bill not only because it sets a timeline for troop withdrawals but also because it's stuffed with billions in non-emergency farm aid, extraneous items for the U.S. Capitol like asbestos removal and guided tours, plus $100 million for security at next year's presidential nominating conventions.

Boehner and members of the GOP leadership team began collecting signatures for the veto letter after last Thursday's White House meeting with the president and gathered more than enough support to sustain a veto in less than three hours. Boehner said he believes virtually all of the 201 House Republicans in the 110th Congress will vote to sustain a veto purely over the extra spending.

Asked Sunday why war spending legislation contained funding for projects like peanut crops and cricket infestations, House Ways and Means Committee Chairman Charles Rangel acknowledged Democratic leaders "needed the votes."

He said the bill lost Democratic support because "people thought we went too far and others because we didn't go far enough. And so a lot of things had to go into a bill that certainly those of us who respect great legislation did not want in there."

FOX News' Major Garrett and Molly Hooper contributed to this report.