Afghanistan's President Ashraf Ghani speaks during a event in Kabul January 1, 2015. [Photo/Agencies]

'REAL APPREHENSION'

When announcing the US withdrawal from Afghanistan on May 27, Obama gave no hint of flexibility, saying the United States would have approximately 9,800 troops there at the start of 2015, roughly half that number at the end of the year, and would be down to "a normal embassy presence" when 2016 ended.

While stressing that the US combat mission in Afghanistan would end in 2014, Obama made two exceptions: targeting the remnants of al Qaeda and training Afghan security forces

However, he has already shifted his May 27 stance in two respects since making the speech last year.

Late last year, Obama decided to keep about 10,800 military personnel in Afghanistan temporarily, 1,000 more than originally planned, due to a shortfall in troops from other nations.

He also quietly authorized a third exception, allowing US troops to act to save Afghan forces "in extremis" from being overwhelmed by the Taliban.

Ghani is expected to visit Washington in the coming months, giving him a chance to make his case for a longer US presence in private with Obama and perhaps also to the US public.

He may find an ally in the US military.

"These are generals who have spent the most important parts of their careers fighting this war and the war in Iraq. They don't want to see all the gains they have made obliterated," said Jonah Blank, a former Senate Foreign Relations Committee staff member now at the Rand Corporation think tank.

"In the upper reaches of the officer corps there is a real apprehension about what happens if we draw down too quickly."