The U.S. should pull troops from Iraq after this summer if the political conditions in the country do not improve, the top Democrat on the Senate Foreign Relations Committee said Sunday.

Sen. Joseph Biden of Delaware, who is aiming for the 2008 presidential race, said the Iraqis must have a constitution that unites fighting factions of the society or "it's game over."

"We can't want peace in Iraq more than the Iraqis want it," Biden said on NBC's "Meet the Press." "We can't want it more than they want it. And if they don't step up to the ball, we're going to be gone."

Biden said if knew what he knows now when Congress voted on the Iraq war resolution, he would have opposed it. "This has been a debacle," he said.

Sen. George Allen, R-Va., said he agrees that it is vitally important for the Iraqis elected in February's parliamentary elections to form a government. But Allen, also a presidential hopeful, said he is unwilling to set a specific deadline.

Allen said the situation among the Kurds, Shiites, Sunnis is "going tough."

"Politically, action needs to be taken," Allen said. "They need to come together and then I think there will be greater confidence on part of the people of Iraq."

Presidential adviser Karl Rove said Saturday that the Bush administration will not pull American troops out of Iraq until victory is achieved, despite the growing number of Democrats urging a withdrawal.

Abandoning Iraq now would signal to U.S. allies that America can't be trusted, Rove said during a Republican fundraiser at Bowling Green State University in Ohio.

"Tyrants in the Middle East would laugh at our failed resolve," he said. "To retreat before victory would be a reckless act."