Washington's special envoy to Afghanistan met with the Taliban in Qatar, the insurgents said Saturday, as efforts intensify to revive a peace process faced with mounting violence and a US troop withdrawal deadline.

The envoy, Zalmay Khalilzad, held talks earlier this week with Afghan leaders in Kabul, including President Ashraf Ghani and Abdullah Abdullah, chair of Afghanistan's High Council for National Reconciliation which oversees the government's talks with the insurgents in Qatar.  

Taliban spokesman Muhamad Naeem tweeted that Khalilzad and the top US general in Afghanistan met with the insurgents' negotiating team in Doha, including Mullah Abdul Ghani Baradar, late Friday.

"Both sides expressed their commitment to the Doha agreement and discussed its full implementation. Likewise, the current situation of Afghanistan and the rapidity and effectiveness of the Intra-Afghan negotiations were discussed," he wrote.

Speculation is rife over America's future in Afghanistan, after the White House announced plans to review a withdrawal deal brokered by Khalilzad and the Taliban in Doha last year.

Under that agreement, the US is set to withdraw from Afghanistan in May, but a surge in fighting has sparked concerns that a speedy exit may unleash greater chaos as peace talks between the Kabul government and Taliban continue to stall. 

The accord states that the US will withdraw all troops from Afghanistan, with the Taliban promising not to allow territory to be used by terrorists -- the original goal of the US invasion following the September 11, 2001 attacks.

Khalilzad's visit marks the first time he has publicly returned to Qatar since US President Joe Biden took office in January and asked him to stay on in his post.