The U.S. general who will oversee the end of the NATO mission in Afghanistan has said there will have to be talks with the Taliban at some stage, BBC News reported.

Gen Joseph Dunford said the international community would need to go on supporting the Afghan army after NATO combat troops leave next year. Without that support, he said, the gains that have been made in democracy and women's rights could be reversed.

Gen Dunford said Afghanistan's progress as a nation was in no way guaranteed.

He is the last commander of NATO's International Security Assistance Force (ISAF), and is expected to remain in the post until the end of next year, when NATO combat troops are scheduled to leave.

Speaking to the BBC in Kunduz, in the north of the country, he warned that progress on important issues could be reversed without further international commitment.

He said: "At this point we have made significant progress, but we are not yet at the point where it is completely sustainable. That really is the focus of effort over the next 18 months. That's why we need to start now - especially with the Afghan security forces - to talk about 2018, not 2014. That period of time will allow these gains to be sustainable."

Next week, the last districts in the country will be handed over to full Afghan government control, with some international troops remaining in a supporting role.

General Dunford said Afghan forces were "getting good enough" to fight the conflict, but stressed that talking to the Taliban was critical for the country's future.

They were not the only enemy, and many criminal groups had joined the complex insurgency, he added.

The warning comes amid a fresh wave of violence in Afghanistan, believed to have been carried out by the Taliban.

On Tuesday, June 11, a suicide bomb attack in Kabul killed at least 16 people and injured more than 40 others outside the Supreme Court.

The previous day, seven insurgents, including suicide bombers, laid siege to the city's main airport for four hours before they were killed.