Afghanistan's president Hamid Karzai has failed to meet a deadline to sign a bilateral security agreement with the United States by the end of 2013.
The US will continue to press Mr Karzai to approve the deal to allow a reduced number of American troops to remain in Afghanistan from 2015.
Without a presidential signature, Washington says it will have to plan for a future in which there would be no American or NATO military presence to combat the Taliban insurgency, the BBC reports.