Sens. Barack Obama and Hillary Rodham Clinton separately declared their support Tuesday for a March 31, 2008 cutoff in funds for the Iraq war, two Democratic presidential front-runners abruptly shifting positions on an issue at the heart of the 2008 race.

The twin announcements came on the eve of a largely symbolic Senate vote on legislation to cut off funds for the war, and as a third presidential contender, Sen. Chris Dodd, D-Conn., said in a campaign commercial it was unfortunate that his White House rivals "will not join me" in supporting the measure.

In a written statement issued in early afternoon, Obama said that after 1,518 days, "the Iraq war rages on, with no sign of a resolution."

The Illinois senator said he would vote for a cutoff in war funding as well as a second bill setting standards for the Iraqi government "not because I believe either is the best answer, but because I want to send a strong statement to the Iraqi government, the president and my Republican colleagues that it's long past time to change course."

A few hours later, a spokesman for Clinton said she, too, would support the measure.

Clinton will cast her votes "to send the president a clear message that it is time to change course, redeploy our troops out of Iraq, and end this war as soon as possible," said Philippe Reines, a spokesman in her Senate office.

The flurry of activity served as prelude to a schedule vote Wednesday on legislation by Sen. Russell Feingold, D-Wis., to require President Bush to begin the "safe, phased withdrawal of U.S. forces" within 120 days.

After March 31, 2008, all funds would be cut off for the deployment of troops in Iraq, with three exceptions: "targeted operations" against al-Qaida and other terrorists; security of U.S. facilities and personnel; training and equipping of Iraqi security forces.

Both Democratic presidential front-runners had previously declined to support proposals ordering the withdrawal of U.S. troops on a mandatory timeline. Clinton, in particular, has spoken out repeatedly against the idea, and drew boos from an audience in June 2006 after criticizing President Bush, then adding, "Nor do I think it is smart strategy to set a date certain. I do not agree that that is in the best interest of our troops or our country."

Nearly a year ago, both she and Obama opposed legislation in the Senate that would have required the withdrawal of all U.S. combat troops from Iraq by July 1, 2007.