The US negotiator on Afghanistan, Zalmay Khalilzad, was in Doha Thursday for shuttle diplomacy between the Afghan government and Taliban negotiators, who are believed to be nearing a compromise on a key sticking point.

Discussions that began in the Qatari capital in mid-September, aimed at ending Afghanistan's 19-year conflict, have stalled over disagreements on how to frame a code of conduct that will guide the broader talks.

The veteran US diplomat is to meet with both teams "to hear updates on their efforts to negotiate a settlement", the US State Department said in a statement before Khalilzad's arrival late Wednesday.

Headline issues, including a ceasefire or the type of governance that will shape Afghanistan's future, have yet to be discussed. But Abdullah Abdullah, chairman of the High Council for National Reconciliation, which is overseeing Kabul's peace push, told AFP Wednesday there could be progress on a row over which interpretation of Islam should be used to frame laws in post-conflict Afghanistan.

The Taliban, who are Sunni hardliners, had insisted on adherence to the Hanafi school of Sunni Islamic jurisprudence, but government negotiators worried this could be used to discriminate against the predominantly Shiite Hazaras and other minorities.

Another contentious topic is how the US-Taliban deal will shape a future peace deal and how it will be referred to. Khalilzad, who brokered Washington's deal with the Taliban in February, is not mediating the talks and has insisted on the importance of "Afghan-to-Afghan reconciliation".

"The Afghan people and international community are watching closely and expect the negotiations to make progress towards producing a roadmap for Afghanistan's political future and a permanent and comprehensive ceasefire," he tweeted before his arrival in Doha.

Despite the hiccups, which have cooled the mood after an optimistic start, both sides are nonetheless committed to pursuing the talks, said Matin Bek, a negotiator on the Afghan team. "Efforts are on the way to move forward and break this impasse," he told AFP Wednesday.

"It takes a lot of courage to sit and leave behind what they (the Taliban) have done, but we are in it to solve it. To end this war," Nader Naderi, a key member of the Afghan negotiating team, said earlier this week.

Although no official meeting between the two sides has taken place in the last three days, discussions are ongoing behind the scenes.