US President Barack Obama has arrived in Afghanistan on a previously unannounced visit.
He is to sign an agreement with Afghan President Hamid Karzai charting future relations with the country.
The agreement will outline the US role in Afghanistan after 2014, when most Nato combat forces are due to pull out.
Mr Obama is also due to give a TV address to Americans back home. The visit comes on the first anniversary of Osama Bin Laden's killing.
It was a year ago that US special forces carried out a raid on Bin Laden's compound in Abbottabad, Pakistan, and killed the leader of the al-Qaeda network.
The US is to designate Afghanistan as a major non-Nato ally, US officials are quoted as saying by Reuters news agency.
Mr Obama will not make specific decisions on further reductions of US forces in Afghanistan until the autumn of 2012, the officials added.
Mr Obama is due to make his TV address from Bagram air base at 23:30 GMT.