Negotiators for the US and the Taliban insurgents have reached "agreements in principle" on key issues for a peace deal that would end 17 years of war in Afghanistan, the top US envoy said Monday.

The statement by US envoy Zalmay Khalilzad followed six days of talks last week with the Taliban in Qatar, where he urged the Islamic insurgent group to enter into direct negotiations with the government of Afghan President Ashraf Ghani.

Khalilzad said in an interview with The New York Times that an agreement in principle was reached with the Taliban on the framework of a peace deal "which still has to be fleshed out" that will see the insurgents commit to guaranteeing that Afghan territory is not used as a "platform for international terrorist groups or individuals."

Former US special representative for Afghanistan and Pakistan James Dobbins says the deal is 'a hopeful sign that negotiations' can begin, but warns the process has 'a number of chasms to cross.'

"First is the Taliban willing to talk to the Afghan government and stop fighting while they do it," said Dobbins.

"Secondly, will the negotiations with the Afghan government succeed in reaching agreement on some new arrangements for governing Afghanistan. And thirdly, will that agreement be implemented. I don't think the US can leave until all of that has been accomplished."

Dobbins was Ambassador to the European Union and is a senior fellow and distinguished chair in Diplomacy and Security at the RAND Corporation.

He also served during the Obama administration's as a special representative for Afghanistan and Pakistan.

"We started negotiating with the Taliban in 2010 but it's been very intermittent," said Dobbins.

"Largely because we kept insisting that the Taliban needed to also talk to the Afghan government and they have consistently refused to do so. If they continue to refuse to do so then this agreement won't mean anything either."