The US envoy for Afghanistan said on Tuesday that the level of violence there was still too high and the Kabul government and Taliban insurgents must work harder towards forging a ceasefire at their peace talks.
Special Representative Zalmay Khalilzad made his comments ahead of flying to Doha to meet with the two sides.
"I return to the region disappointed that despite commitments to lower violence, it has not happened. The window to achieve a political settlement will not stay open forever," he said in a tweet.
The talks between a government delegation and the delegation have been going on in Doha since mid-September but progress has been slow and diplomats and officials have warned that rising violence back home is sapping trust.
The two sides are often at odds on even the most basic issues.
"The sides must move past procedure and into substantive negotiations," said Khalilzad's office in a statement on Tuesday.
There needed to be "an agreement on a reduction of violence leading to a permanent and comprehensive ceasefire," he said.
Last week, Khalilzad said he had struck an agreement with the Taliban to "re-set" their commitments under a troop withdrawal deal and reduce the number of casualties in the conflict.
The deal in February between the United States and the Taliban paved the way for foreign forces to leave Afghanistan by May 2021 in exchange for counter-terrorism guarantees from the Taliban, which agreed to negotiate a permanent ceasefire and a power-sharing formula with the Afghan government.
The intra-Afghan talks have taken on increased significance against the backdrop of the US election, with President Donald Trump keen to end the nearly two-decade-long US war in Afghanistan and see US troops home by Christmas - well ahead of the proposed withdrawal timeline.
Published 27 October 2020, 16:33 IST