In a series of interviews from Beijing with US network and cable channels, Mr Obama said a decision on troop numbers and a refined strategy was close.

He told CNN he believed his Afghan policy needed to include an endgame because ''unless you impose that kind of discipline, [US policy] could end up leading to a multiyear occupation that won't serve the interests of the United States''.

Senior military and Administration officials said Mr Obama was not asking for firm, publicly declared handover dates like those in early Iraq war plans.

Instead, the officials said, the Administration wants the Pentagon to identify important milestones for Afghanistan to reach, in its governance and the capability of its security forces, and then give a rough sense of when each objective is likely to be achieved. Reaching these goals would allow the US role to shift away from direct combat, allowing troop levels to decline.

''What the White House wants is a strategic glide path that gives a sense of the path ahead and the time it will take to meet each specific target,'' a military official said. ''It's not a hard-and-fast timetable for withdrawal.''

The President said his goal was to ensure that his successor does not inherit the conflict.

''My preference would be not to hand off anything to the next president. One of the things I'd like is the next president to come in and say, 'I've got a clean slate and I can put my vision forward','' he said.

He did not indicate whether he was thinking about the end of one term in office or two.

Mr Obama gave only lukewarm support to Afghanistan's President, Hamid Karzai, whose recent re-election was tainted by fraud and who has been widely criticised for failing to tackle rampant corruption. Mr Karzai was sworn in for a second term yesterday.