Disputes over the size of delegations have roiled critical peace talks between the Afghan government and the Taliban, with new talks in Qatar now suspended and Washington urging both sides to return to the table.
The talks, which had been scheduled for April 19, were considered a significant first step toward finding a negotiated end to the war in Afghanistan and the eventual withdrawal of U.S. troops.
But a statement released April 18 by the Afghan government blamed the Qatari government for the disruption.
The head of the organization hosting the talks in Doha, however, said the dispute stemmed from disagreement 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 earlier in the week had announced a list of 250 people, including government figures, to attend the so-called intra-Afghan dialogue in Doha.
The Taliban criticized the lengthy list, saying that they would not meet with so many people.
The Taliban also insisted they would not be negotiating with Kabul at the conference.
The list was also criticized by some powerful opposition figures, including the powerful former warlord, Atta Mohammad Noor, who said it was not inclusive.
The U.S. Special Representative to Afghanistan, Zalmay Khalilzad, said he was disappointed by the delay.
"We're in touch with all parties and encouraged that everyone remains committed to dialogue," the envoy said in a post to 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 United States has been holding separate bilateral peace negotiations with the Taliban in Doha as part of a months-long peace push.
In Afghanistan, meanwhile, the Taliban have launched their so-called spring offensive, unleashing violence in many parts of the country.
The militants now control or influence about half the country, and last year was the deadliest yet for civilians.