Some NATO officials fear a rise in violence could make it hard to meet the target date set by Afghan President Hamid Karzai for the security handover, which would leave a vastly reduced number of foreign troops in a training and support role.

But President Barack Obama lifted hopes the target date would be met by saying for the first time that his aim was to halt major U.S. combat operations by the end of 2014 and significantly reduce the number of U.S. troops there.

"Today marks the beginning of a new phase in our mission in Afghanistan," NATO Secretary-General Anders Fogh Rasmussen told an alliance summit in Lisbon attended by the Afghan president and 48 countries with troops in Afghanistan.

"I don't foresee ISAF (International Security Assistance Force) troops in a combat role beyond 2014, provided of course that the security situation allows us to move into a more supportive role."

Reuters