Watch part 2

Amid criticism from some US politicians that the president's mid-2011 deadline to begin withdrawing US troops from Afghanistan sends the wrong message to allies and foes, Admiral Mike Mullen, the chairman of the joint chiefs of staff, has defended the deadline.

The highest-ranking US military says that there is as yet no decision on "how many [troops] would come out or what the pace would be or when it would end".

"But," he tells Al Jazeera's Shihab Rattansi, the 18-month countdown "is meant to be a clear signal that the Afghans have to take control here as well".

Source: Al Jazeera