According to President Barack Obama's own timetable, US troops will begin a gradual and phased pullback from Afghanistan in just seven months time.
Is that feasible given the state of the Afghan conflict and the Karzai government?
The former adviser to three US presidents, Bruce Ridel, tells Stephen Sackur why he believes President Obama's most difficult challenge is to break Pakistan's relationship with the Taliban.
You can watch the full interview on Wednesday 5 January 2011 on BBC World News at 0430, 0930, 1530 & 2130 GMT and on BBC News at 0230, 0430 and 2330.
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