Levin, in appearance on CBS's "Face The Nation," said creating an official withdrawal plan for U.S. troops stationed in Iraq is the best way to get the Iraqi government to move forward.

"We should insist that there be a timetable because there is no other way to force the Iraqi government to work out those political settlements, which are absolutely essential to end the conflict," Levin said.

U.S. Sen. Richard Lugar, R-Ind., said such withdrawals were slowly becoming more likely to occur given the need for military power elsewhere in the world.

"The demand for troops out there is intense," Lugar said. "The battles on the border with Pakistan, with the al-Qaida forces assisted by the Taliban, are a source of more killing of American troops right now than anything occurring in Iraq."

The withdrawal discussion comes as President George Bush's administration is facing increased criticism regarding the controversial war in Iraq, CBS said.