* Gates leaves door open to post-2011 military presence
* Former U.S. general says maybe "thousands" needed
* Iraqi commander wants U.S. troops to stay until 2020
By Ross Colvin
WASHINGTON, Aug 19 (Reuters) - The United States is on track to draw down its forces in Iraq to 50,000 by Aug. 31, but there are doubts President Barack Obama can fulfill his pledge to withdraw all U.S. troops by the end of 2011.
As a presidential candidate Obama campaigned to end the now seven-year-old war responsibly, and as president he has been explicit in his assurances to Americans that not a single U.S. service member will remain in Iraq come Jan. 1, 2012.
Easier said than done.
While violence has dipped sharply since the height of sectarian warfare from 2006-2007, Iraq remains fragile and its leaders have not resolved a number of politically explosive issues that could easily trigger renewed fighting.
The United States wants a stable, friendly Iraq, and analysts are skeptical Obama will do anything to jeopardize that.
Iraq's military chief, the former U.S. general who oversaw the training of Iraq's security forces, and U.S. officials who negotiated the current U.S.-Iraqi military pact are among those who say a U.S. military presence will be needed beyond 2011.
Obama's defense secretary, Robert Gates, left the door open to that possibility in comments last week while emphasizing that Iraq's new government, still to be formed after an inconclusive election in March, would first have to ask.
"If a new government is formed there and they want to talk about beyond 2011, we're obviously open to that discussion," Gates said."
His comments were likely not welcomed in the White House, which is carefully sticking to its Iraq talking point for voters before tough congressional elections in November -- the president is keeping his promise to withdraw all U.S. troops by the end of 2011.
There have been more than 4,400 U.S. military deaths in Iraq since the U.S.-led invasion in 2003 that toppled dictator Saddam Hussein.
The U.S.-Iraq military pact that came into force in 2009 provides the legal basis for U.S. troops to be in Iraq. Under the agreement, all U.S. troops must be out by 2012. But U.S. negotiators say that even as the pact was being negotiated, it was considered likely it would be quietly revised later to allow a longer-term, although much smaller, force to remain.
There are currently 56,000 U.S. troops in Iraq, down from about 140,000 when Obama took office in January 2009.
With opinion polls showing Americans tired of nearly a decade of war in Afghanistan and Iraq, any decision to extend U.S. military involvement in Iraq would be enormously risky for Obama, who is up for re-election in 2012.
He would almost certainly face a backlash from fellow Democrats in Congress and from the left wing of his party, which is already disenchanted with him.
Obama may be unwilling to alienate his party base as he heads into an election year, or he could decide it is in his country's strategic interests to keep troops longer in Iraq -- again, only if a new Iraqi government asks.
"The president has proven to be a very pragmatic leader. As conditions change, he has adapted his positions in Afghanistan and Iraq. So, I think he wants to hold his promise until conditions will dictate otherwise," said retired Lieutenant-General James Dubik, who oversaw the training of Iraqi security forces from 2007 to 2008.
"A discussion after 2011 is not just what does Iraq need, but what is in our strategic best interest," said Dubik, now with the Institute for the Study of War.
Dubik said post-2011 Iraq would still need U.S. and Western help in modernizing its forces and training them to use M1 Abrams tanks, F-16s and other sophisticated military hardware it is buying from the United States.
He also sees the need for a peacekeeping-like force to stabilize areas where there are still tensions, for example along the southern border of Kurdistan, and possibly troops to assist in counterterrorism operations.
The U.S. commander in Iraq, General Ray Odierno, has singled out ethnic tensions between Arabs and Kurds in northern Iraq as the biggest threat to the country's stability.
"I hate to put a number on it but it's going to be in the thousands," Dubik said, when asked how many personnel would be required to fulfill the various tasks he had outlined.
Iraq's military commander, Lieutenant-General Babakir Zebari, caused consternation last week when he said his troops would not be ready to protect the country until 2020, and that the United States should keep its forces there until then.
The Obama administration says only that it plans to set up an "office of security cooperation" at the U.S. Embassy in Baghdad. Its staff will help train Iraqi military personnel and coordinate weapons purchases but will number no more than a few dozen, or "maybe in the hundreds."
"For a very long period of time, we're going to be on the ground, even if it's solely in support of its (Iraq's) U.S. weapons systems," Ryan Crocker, former U.S. ambassador to Iraq, told The New York Times.
Then there are the persistent fears that Iraq remains vulnerable to a resurgence of the sectarian violence between majority Shi'ites and Sunni Muslims that tipped the country into near-civil war in 2006 and 2007.
"There are so many debts to be paid on both sides and so much accumulated fear that the other side is going to cash in on those debts. It is very, very easy for these things to spiral upward," said Stephen Biddle, a military analyst at the Council on Foreign Relations and a former adviser to General David Petraeus when he was U.S. military commander in Iraq.
Biddle is among those calling for the United States to withdraw its troops gradually from Iraq over a period of years, following the model of the NATO-led peacekeeping operation in the Balkans.
Whatever Obama decides, the United States will almost certainly need to negotiate a new military pact, known as a status of forces, or SOFA, agreement with Iraq so that, at the very least, Marine guards can be deployed at the U.S. Embassy.
"If the (current) SOFA is followed, there will be fewer uniformed Americans in Iraq on January 1, 2012, than there are in Great Britain," Biddle said. (Editing by Patricia Wilson and Peter Cooney)