WASHINGTON (CNN) -- With the four-year anniversary of the Iraq war looming, Senators agreed Wednesday to allow debate on a Democratic resolution that sets April 1, 2008, as a target date for ending the U.S. combat mission in Iraq.

The issue passed with a procedural vote of 89-9. The resolution could be discussed for the rest of the week.

The target date, Sen. John Kerry of Massachusetts said at a news conference, "is a date that leaves enormous discretion in the presidents' hands according to the Constitution, which is appropriate, to be able to finish the job of training and get our troops home."

Today, he said, U.S. forces are "acting as a security blanket for politicians who are squabbling among themselves in Iraq."

The United States invaded Iraq on March 19, 2003.

Kerry was joined by several other Democrats, including Senate Majority Leader Harry Reid.

"What we are doing in Iraq is policing an intractable civil war," Reid said. "We believe the president should be held accountable for a new direction in Iraq."

Sen. Carl Levin of Michigan said a "comprehensive political, economic, diplomatic strategy is part of the plan."

On Tuesday, Senate Republicans emerged from a closed-door strategy session to say they had dropped their opposition to beginning debate on the resolution.