Although there was no official statement from either side, the head of the organisation hosting the talks in Doha said they had been derailed by a row over the size and composition of the respective delegations.

"This unfortunate postponement is necessary to build further consensus as to who should participate in the conference," Sultan Barakat, of the Center for Conflict and Humanitarian Studies, said in a statement.

President Ashraf Ghani's administration had on Tuesday announced a list of 250 people from all walks of Afghan life, including government figures, who it wanted to send to the so-called intra-Afghan dialogue in Doha beginning Saturday.

But the Taliban poured scorn on the lengthy list, saying it was not "normal" and that they had "no plans" to meet with so many people.

The Taliban -- who see Ghani as a US stooge and his government as a puppet regime -- also insisted they would not be negotiating with Kabul at the conference.

US Special Representative to Afghanistan Zalmay Khalilzad said he was "disappointed Qatar's intra-Afghan initiative has been delayed".

"We're in touch with all parties and encouraged that everyone remains committed to dialogue," the envoy wrote on Twitter.

"I urge all sides to seize the moment and put things back on track by agreeing to a participant list that speaks for all Afghans."

The US has been holding separate bilateral peace negotiations with the Taliban in Doha as part of a months-long peace push led by Washington.

The developments come as fresh violence rips across Afghanistan, with the Taliban launching their so-called spring offensive.

The militants now control or influence about half the country, and last year was the deadliest yet for civilians.