Our correspondent says the US president is likely to discuss the size of the force that remains, and whether they are there to fight the Taliban or shift their primary focus to tackling al-Qaeda.

BBC: British soldier killed by Afghan army gunman in Helmand

The BBC's Quentin Sommerville in Kabul says the US president is likely to discuss the size of the force that remains, and whether they are there to fight the Taliban or shift their primary focus to tackling al-Qaeda.

BBC: Afghan 'zero option' raised as Karzai set for Obama

Moaz al-Khatib, the Syrian opposition leader, appeared underwhelmed by the US shift.

BBC: Frustration forces Western shift on Syria

This political shift may well have helped to persuade Mr Clinton and Vice-President Al Gore that it was time to show willing, despite the Pentagon's reservations.

ECONOMIST: The new convert