The transatlantic alliance, which maintains a training mission in Afghanistan after ending combat operations there in 2014, demanded the Taliban curb violence to allow talks to start.

The call comes after the militants dismissed a government call for a Ramadan ceasefire as "not rational" and as they ramp up attacks on security forces.

"The current level of violence caused by the Taliban is not acceptable," the North Atlantic Council, NATO's ruling body, said in a statement.

"We call urgently on the Taliban to reduce violence and create the conditions conducive to commence negotiations."

Under a landmark US-Taliban deal signed earlier this year, the Afghan government and the insurgents were by now supposed to have concluded a prisoner swap and started talks aimed at bringing about a comprehensive ceasefire.

But the Taliban have pulled negotiators out of talks amid a dispute over the prisoner exchange.

The situation is complicated by an ongoing feud between Afghan President Ashraf Ghani and his rival Abdullah Abdullah -- who has also proclaimed himself president after last year's controversial election.

NATO said Afghanistan had a "historic opportunity" to end its long conflict and called on the two sides to reconcile.

"We call urgently upon Afghanistan's political leaders and their supporters to come together to resolve their differences and form an inclusive government," it said.

"Afghanistan's political actors must seize this opportunity for peace."

American and other foreign forces have pledged to quit Afghanistan by July 2021 provided the Taliban stick to several security guarantees and hold talks with the government.

NATO insists the departure of its forces will depend on conditions on the ground, and it will not allow Afghanistan to become a safe haven for terror groups.