The White House says President Barack Obama has ordered the Pentagon to prepare plans to withdraw U.S. troops from Afghanistan by the end of this year.
A White House statement said Obama ordered the move because Afghanistan's President Hamid Karzai has indicated he is unlikely to sign a Bilateral Security Agreement that would allow the United States to keep troops in Afghanistan after this year.
The statement added that should the Afghan government sign the accord, the United States remained ready to keep a "limited" force in Afghanistan after 2014 to focus on training Afghan forces and conducting antiterrorism missions.
The statement said Obama had spoken with Karzai on February 25 by telephone.
Karzai, who is due to leave office after Afghanistan's April elections, has sought several concessions from Washington over the security pact.
In other news, Afghan officials say at least eight people are dead and dozens of others are injured following a suicide bomb attack in the southern province of Oruzgan.
Officials said the explosion took place on February 25 in the provincial capital, Tirin Kot.
Reports say civilians were among the victims. It wasn't immediately clear who was responsible for the blast.
Elsewhere, officials said three people were killed and three others injured in a bomb blast in the Marjah district of the southern province of Helmand.
It was not immediately apparent who was behind the attack.
With reporting by dpa and AFP