Image copyright AFP Image caption The US has about 14,000 troops in Afghanistan and is part of a Nato mission there

The top US envoy seeking to broker peace in Afghanistan has met one of the Taliban's co-founders for the first time, as the latest round of talks get under way in Qatar.

Special representative Zalmay Khalilzad said he held a working lunch with Mullah Abdul Ghani Baradar before "moving on to talks".

Mullah Baradar was recently released from a Pakistani prison.

His presence in Qatar is thought to improve the chances of a deal.

Last month's US-Taliban talks in Qatar made progress in ending 17 years of conflict in Afghanistan, the US said.

US special envoy Zalmay Khalilzad said the January talks had been "more productive than they have been in the past" but added there were a number of issues still to work out.

He said a "draft framework" of a peace deal had been agreed, based on commitments by the US to withdraw international forces from Afghanistan, and from the Taliban not to allow jihadist groups to operate in the country.

The Taliban also said progress had been made in the negotiations. However, a spokesman added that talks about "unsolved matters" would continue.

The Taliban have 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.

Mullah Baradar, a deputy to Taliban leader Hibatullah Akhunzada, was put in charge of the Taliban political office in Qatar in January but until now has remained in Pakistan and has not made any public appearances.

He served in a number of key roles within the Taliban, until he was detained by Pakistani authorities in 2010.

A senior Taliban figure told the BBC that Mullah Baradar's authority within the group to make decisions could help "speed up the peace process".

Mr Khalilzad has suggested this is the case. He tweeted that he was this time meeting "with a more authoritative Taliban delegation", adding that it "could be a significant moment".

After last month's talks, Taliban sources told the BBC that the two sides had agreed to form committees to address two key issues in detail: the withdrawal of foreign forces and how the Taliban would in turn implement a commitment to prevent groups like al-Qaeda and Islamic State from using Afghanistan as a base in future.

Obstacles ahead

by Secunder Kermani, BBC Afghanistan correspondent, in Doha

Mullah Baradar isn't the only senior figure from the group attending the talks in Doha for the first time. Also here is Amir Khan Motaqi, chief of staff to the Taliban supreme leader. Their presence seems to indicate how seriously the Taliban are taking these discussions.

But there are still major obstacles ahead.

It seems Afghan President Ashraf Ghani's administration is being deliberately sidelined by the Taliban who have so far refused to talk to them. Yet it's hard to see how a deal could be done without their involvement.

The absence of talks between the Taliban and the Kabul government also means there's been no official discussion of what a post-peace Afghanistan would look like. Would it be a democracy? Would women have the same rights they have now?

There's an argument that while progress has been made, so far the Taliban are yet to make any major concessions. Their promise not to allow other jihadists to operate in Afghanistan isn't new. American officials will hope this beefed up Taliban negotiating team will have the authority and willingness to show some flexibility.

The Taliban's power and reach have surged since foreign combat troops left Afghanistan in 2014.

Media playback is unsupported on your device Media caption The BBC is given rare access to see life under the Taliban

Last month, Afghan President Ashraf Ghani said more than 45,000 members of the country's security forces had been killed since he became leader 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.

On Sunday UN figures showed that more civilians were killed last year in Afghanistan than at any time since records began.

In December, reports emerged that the US was planning to withdraw about 7,000 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 Islamic 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.