During an hour-long conversation Downing Street says David Cameron also discussed Syria, Iran and the Middle East Peace Process with President Obama:
On Afghanistan, they discussed progress on the plan to hand security responsibility from the International Security Assistance Force (ISAF) to the Afghan National Security Forces, and agreed that the NATO strategy to withdraw combat troops from Afghanistan by the end of 2014 was on track.
This would present further opportunities for ISAF countries to bring troops home next year and they agreed to stay in close touch as detailed plans develop.
They also agreed on joint work to strengthen the political process, particularly supporting Afghanistan and her neighbours to work together for stability, building on the trilateral discussions with Pakistan led by the UK.
A Conservative backbencher has said that the government's decision to withdraw troops from Afghanistan will be "difficult and dangerous".
ITV News understands that Britain's withdrawal from Afghanistan may be speeded up with troop numbers almost halved in the next year.