Domenici, a six-term member of the Senate who is up for re-election in 2008, endorsed legislation designed to withdraw nearly all U.S. troops from Iraq by March 2008, The Washington Post reported.
Domenici is the fourth senior Senate Republican to challenge Bush's war strategy in recent weeks. Republican Sens. Richard Lugar of Indiana, George Voinovich of Ohio and John Warner of Ohio have recently said they favor a change in policy in Iraq.
Domenici told reporters in Albuquerque Thursday he would co-sponsor legislation to adopt the recommendations of the Iraq Study Group -- which called for withdrawing all but a limited number of troops from in Iraq.
"I have carefully studied the Iraq situation, and believe we cannot continue asking our troops to sacrifice indefinitely while the Iraqi government is not making measurable progress to move its country forward," he said.
Domenici said he does not support an immediate withdrawal.
"But I do support a new strategy that will move our troops out of combat operations and on the path to coming home," he said.