The US special representative for Afghanistan on Saturday hailed "significant progress" in talks with the Taliban to end the country's long-running war.
Zalmay Khalilzad has held almost a week of negotiations with Taliban representatives from the group's political office in Doha, raising hopes of progress towards peace.
"After six days in Doha, I'm headed to Afghanistan for consultations. Meetings here were more productive than they have been in the past. We made significant progress on vital issues," Mr Khalilzad said on Twitter.
Mr Khalilzad, a former ambassador to Afghanistan who has held several rounds of talks with the Taliban since he was appointed in September, did not provide details of any breakthrough but said negotiations would resume soon.
"We have a number of issues left to work out. Nothing is agreed until everything is agreed, and 'everything' must include an intra-Afghan dialogue and comprehensive ceasefire," he tweeted.
Taliban negotiators had said earlier that they were close to finalising a draft peace agreement with the United States.
Hoping to secure the withdrawal of foreign forces from Afghanistan within 18 months, the Taliban negotiators have offered the US assurances that the country will not be used by Al Qaeda and ISIS militants to attack the US and its allies, Taliban sources said on Saturday.
The US's longest war began with its invasion to oust the Taliban from power following the September 11, 2001 terror attacks on the US. The attacks were masterminded by Osama bin Laden, the Al Qaeda leader who was then sheltering in Afghanistan.
Mr Khalilzad will now brief Afghan President Ashraf Ghani in Kabul, sources and a diplomat told Reuters.
The peace talks in the Qatari capital, initially slated for two days, continued despite Taliban representatives staging a brief walkout on Friday over differences with Mr Khalilzad.
Two senior Taliban officials in Afghanistan who are privy to the negotiations said momentum was building following the appointment on Thursday of Mullah Abdul Ghani Baradar as the political leader of the hardline Islamist group.
Mr Baradar, released from a prison in Pakistan last year, is expected to fly to Qatar to join the talks – a move they believe will be welcomed by a US side keen to talk to senior Taliban figures.
"He is expected to join soon," one of the senior Taliban officials in Afghanistan said.
A co-founder of the group, he was a close friend of the reclusive former Taliban leader, Mullah Mohammad Omar, who gave him his nom de guerre, “Baradar” or “brother”.
His appointment marks a new push to bring Taliban out of the political and diplomatic shadows, with several other officials being appointed to oversee education, mining and health issues.
The Taliban currently controls nearly half of the country and are widely seen as being more powerful than at any point since the beginning of the US invasion to topple them. Despite the ongoing peace talks, the group has continued carrying out near daily attacks against the western-backed Afghan government and its security forces. Last Tuesday, Taliban militants carried out a complex attack on a military base east of Kabul in which dozens of Afghan soldiers were killed.
President Ghani said last week that 45,000 members of the country’s security forces had been killed since he took office in the fall of 2014.
Whether the US have accepted the proposed provisions is unclear but Taliban sources said they were willing to acquiesce to a key early demand of Washington that the country not become a safe-haven for terrorists planning to attack the West.
President Donald Trump has expressed eagerness to bring home his troops, and was reported to be considering a halving of the remaining 14,000 US forces still in Afghanistan.
The Taliban say they will finalise a timeline for a ceasefire in Afghanistan but will only open talks with Afghan representatives once the ceasefire is implemented. The Taliban views the government in Kabul as a puppet of Washington.
The Taliban is seeking the formation of an interim government in which it expects to play a role once a ceasefire is in effect.
Other clauses include a deal over the exchange and release of prisoners from the warring sides, and the removal of an international travel ban on several Taliban leaders by the US, the Taliban sources said.
Taliban sources also said Baloch separatists militants would not be allowed to use Afghan soil to attack Pakistan.
