On Saturday, President Donald Trump abruptly cancelled an imminent and then secret summit with Taliban leaders and Afghan President Ashraf Ghani on a draft accord that would see the US withdraw thousands of troops.

The move appeared to end a year of negotiations between Washington and the insurgents, although US Secretary of State Mike Pompeo later left the door open for a return to talks.

NATO, which has some 16,000 troops in Afghanistan to train and advise local forces, insisted it would remain in the country as long as needed.

"NATO's focus remains unchanged: to make the Afghan security forces stronger so that they can fight international terrorism and create the conditions for peace," an alliance official told AFP.

"NATO will stay in Afghanistan for as long as necessary to ensure the country never again becomes a safe haven for international terrorists."

Last week, alliance Secretary General Jens Stoltenberg said he supported US efforts to find peace in Afghanistan, which has been racked by conflict for four decades.