By Andrew Gray
WASHINGTON (Reuters) - U.S. military planners have drawn up three options to allow President Barack Obama to withdraw U.S. combat troops from Iraq, with senior commanders favouring the slowest of the three, officials said on Saturday.
The timelines under discussion are 16 months, proposed by Obama as a centrepiece of his presidential campaign, 19 months and 23 months, the officials said.
"The focus of the effort is on those three options," said a U.S. official familiar with the process.
A U.S. defence official said U.S. Army generals Ray Odierno, the top U.S. commander in Iraq, and David Petraeus, the head of U.S. Central Command, favoured the 23-month option.
"Odierno and Petraeus have said that we really need 23 months to do this without jeopardizing the security gains that we've secured," the official said.
Both officials, who spokes on condition of anonymity because of the sensitivity of the issue, said they did not believe the options had been presented to Obama yet.
Obama made opposition to the Iraq war a central plank of his campaign platform.
He suggested all U.S. combat troops would be out of the country in the first 16 months of his administration. But he has also pledged to listen to the advice of commanders.
Obama has said the war in Afghanistan should be the U.S. military's priority and promised to add to the 36,000-strong U.S. force there battling a growing insurgency.
The United States has around 144,000 troops in Iraq, where violence has declined dramatically in the past year and a half, following several years of heavy bloodshed that brought the country to the brink of all-out civil war.
U.S. commanders have repeatedly cautioned against withdrawing troops from Iraq too quickly, arguing that the country remains fragile.
A senior White House official played down any differences between the president and military commanders.
"There's been a very good back and forth in a very logical process that has allowed the president to hear from commanders and forces at all levels," the official said.
"Fact is that they are coming to a meeting of the minds on troops and on the need for a diplomatic and political strategy to end the war in Iraq and ease the strain on the troops and their families," the official added.
Even once all U.S. forces designated as combat troops leave Iraq, Obama has said a residual force would remain to train Iraqi security personnel, protect U.S. diplomats and conduct counterterrorism missions.
That force is likely to consist of tens of thousands of troops, military officials and analysts say.
Under a pact between Washington and Baghdad sealed late last year as the Bush administration prepared to leave office, all U.S. forces are to leave the country by the end of 2011.
U.S. officials have raised the prospect, however, that U.S. troops could remain longer with the agreement of Iraqi authorities to support the country's own security forces.
(Additional reporting by Jeff Mason; editing by Eric Beech)