Washington: American combat troops could stay in war-torn Afghanistan beyond the 2014 deadline set by President Barack Obama for their pullout if Kabul sought delaying their withdrawal, the US Ambassador has said.

The Ambassador, Ryan Crocker said if the Afghan government wanted American troops to stay longer, the withdrawal could be slowed.

"They would have to ask for it," he said. "I could certainly see us saying, 'Yeah, makes sense.' "

He emphasised, however, that no such decision had been made. White House officials said that Crocker's comments were consistent with its previously stated position.

"The President never excluded the possibility that there would be some US forces here, but he stressed that security would be under Afghan lead by 2014," said the embassy spokeswoman, Eileen O'Connor. "The President has always spoken of a responsible winding down of the efforts here, so talk of the possibility of some troops still being here post-2014 is not a change in policy."

But Crocker's comments were an explicit acknowledgment that the post-2014 forces may include combat troops, not just the trainers and advisers who had been publicly mentioned before.

His comments came as the administration was engaged in discussions with the Afghan government on arrangements after 2014.

At a conference in Bonn, Germany, last week, Afghan President Hamid Karzai and other Afghan officials called for political and military support for at least another decade.

In June, Obama announced that American troop withdrawals would begin the following month, with 10,000 of the roughly 101,000 American troops then in the country to leave by December 31, and an additional 23,000 to follow by the summer of 2012.

"We are on a timeline, as you know," Crocker said. "Ten thousand out by the end of the year, that is being met." With the additional 23,000 by September 2012, he added, "that basically recovers the surge" — the reinforcements Obama ordered two years ago.

"Beyond that, there are no decisions," he said, adding, "And as far as I'm aware, there are no formal recommendations yet."

Asked if that meant that the United States would not necessarily withdraw all combat troops by 2014, Crocker said, "I don't know what we're going to be doing in 2014."