FACTBOX: Presidential candidates on Iraq withdrawal

(Reuters) - Both Democrats running for U.S. president have promised to pull troops from Iraq, but some analysts and defense officials question whether either would fulfill that pledge if elected. Here are some statements from the candidates about withdrawal.

* Democratic candidate Hillary Clinton has said the United States could start withdrawing troops within 60 days of her taking office next January and that it was up to the Iraqis to take responsibility for their country's future.

"We cannot win their civil war. There is no military solution," Clinton has said.

* Democratic candidate Barack Obama has promised that if elected he would immediately begin withdrawing troops in a process that could last 16 months, leaving only forces to guard the U.S. Embassy and "a counterterrorism force to strike al Qaeda if it forms a base that the Iraqis cannot destroy."

He has criticized Republican candidate John McCain for not defining success in Iraq. "For him to argue that -- which he has repeatedly -- that any suggestion that we withdraw troops is surrender, that implies that, you know, we will be there as long as he thinks it's necessary for us to be there."

* McCain has said U.S. troops should remain in Iraq for many years but that progress in the war would mean the United States could stand down from a combat posture "in a relatively short period of time."

He has said a premature troop withdrawal would dramatically enhance Iranian influence in the region.

"If we pull out of Iraq ... then obviously the Iranian influence is dramatically increased, al Qaeda has greater influence and endangers the region dramatically, and the United States' image and security challenges are dramatically increased," he has said.

(Compiled by Donna Smith and Kristin Roberts; Editing by David Alexander and David Wiessler)