The US and the Afghan Taliban have made "significant progress" in talks aimed at ending the 17-year-old conflict in Afghanistan, the US envoy has said.
In a series of tweets, Zalmay Khalilzad did not give details but said the unprecedented six days of talks in Qatar were "more productive than they have been in the past".
He said he was on his way to Kabul to consult Afghan government officials.
Earlier, Taliban sources said the two sides had finalised a draft agreement.
The deal calls for a withdrawal of foreign forces in return for assurances that al-Qaeda and the Islamic State (IS) group will not be allowed to use Afghanistan as a base, the sources said.
Mr Khalilzad said talks with the Taliban would continue and that nothing had been finalised.
2/3. Will build on the momentum and resume talks shortly. 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.— U.S. Special Representative Zalmay Khalilzad (@US4AfghanPeace) January 26, 2019
The Taliban has so far refused to hold direct talks with Afghan officials, whom they dismiss as "puppets".
They say they will only begin negotiations with the government once a firm date for the withdrawal of US troops has been agreed.
Taliban sources quoted by Reuters said the key agreements envisaged foreign forces withdrawing within 18 months of the deal being signed.
In return, the Taliban offered assurances that Afghanistan would not be used by al-Qaeda and IS as a base to attack the US.
The two sides have also agreed on other sticking points including the exchange of prisoners and the lifting of travel bans on some Taliban leaders, Reuters reported.
Afghan President Ashraf Ghani has previously said that the Taliban could be recognised as a political party if they accepted a ceasefire and recognised the country's constitution.
In December, reports emerged that the US was planning to withdraw about 7000 troops - roughly half the remaining US military presence in the country.
Analysts warned that such a withdrawal could offer the Taliban a propaganda victory.
Who are the Taliban?
The Taliban emerged in the early 1990s following the withdrawal of Soviet troops from Afghanistan, shortly before the demise of the Soviet Union.
The militants ruled Afghanistan from 1996 to 2001, imposing a brutal version of Sharia law that included public executions and amputations, and the banning of women from public life.
They were driven from power by US-led troops following the 9/11 attacks which Washington blamed on al-Qaeda militants sheltered by the Taliban.
The Taliban's power and reach have surged since foreign combat troops left Afghanistan in 2014.
It is estimated that about 15 million people - half the Afghan population - are living in areas either controlled by the Taliban or where the militants are openly present and regularly mount attacks.