Obama: From the spring 'troops to have new mission'

US President Barack Obama has said that starting in the spring, US troops in Afghanistan will transition into a support role to train, advise and assist Afghan forces.

Speaking at a joint briefing with Afghan President Hamid Karzai, Mr Obama said it would represent a "historic moment" on the road to full Afghan sovereignty.

Mr Obama said "most" combat operations would cease as US troops adopted their new mission.

The leaders also raised the possibility that some troops could stay in Afghanistan after the end of the next year, but did not discuss numbers.