DOHA, Qatar — Organizers canceled talks between Afghan leaders and Taliban insurgents that were scheduled to begin Friday, dealing a major setback to a U.S.-led peace process aimed at ending nearly 18 years of warfare.

The first talks between the two sides were postponed Thursday, then officially called off by sponsors in the Qatari capital, amid a rash of disputes among Afghan officials, Taliban leaders and Qatari meeting hosts over the size and composition of the Afghan delegation.

There was no indication when the talks would be rescheduled, but it appeared unlikely in the immediate future. The peace process has failed to make progress in part because the Taliban had refused to meet with Afghan officials until now.

“Despite tireless and well-intentioned efforts of all parties, a shared understanding on how to achieve inclusivity couldn’t be reached,” tweeted Sultan Barakat, a scholar in Doha whose institute organized the talks. “This doesn’t reflect a lack of will to deliver #peace but clearly the moment is not yet right.”

Although no Afghans traveled here from Kabul for the canceled talks, a group of about 20 invited delegates were Afghan emigres in Europe who were already en route to Doha and arrived late Thursday. Several said Friday that they blamed the Ghani government for the collapse of the talks, but they were expected to meet privately with some Taliban representatives here on Saturday.

In Kabul, the government of President Ashraf Ghani issued a statement Friday morning that blamed the government of Qatar for not accepting a list of proposed Afghan delegates and instead proposing a list that was “not balanced” and “a disrespect to the national will of the Afghan people.”

There was no immediate comment on the cancellation from the Taliban.

Officials in Kabul had announced a final list of 250 delegates on Tuesday that included politicians and civic leaders from across Afghan society, but Taliban officials objected to its large and unwieldy size, prompting a hurried effort to pare down the delegation. But by late Thursday, that effort had collapsed amid arguments over who should be included or excluded.

The planned meeting in Doha had been widely hailed as a potential first step toward peace talks between the Taliban insurgents and their fellow Afghans. The Taliban has long refused to recognize the Kabul government while holding peace discussions with U.S. officials in this Persian Gulf sheikhdom.

One aide to Ghani, speaking on the condition of anonymity because of the sensitive topic, said Thursday the Afghan delegation’s trip to Doha was being delayed because the Taliban representatives and their host, the government of Qatar, wanted some individuals removed from the delegation “in order to make it weak.”

Meanwhile, some delegates voluntarily withdrew Thursday from the planned talks, including one senior Afghan official who expressed anger at Taliban statements ridiculing the Afghan delegation and accused the insurgents of trying to sabotage the talks.

“Taliban are the only & the biggest obstacle to peace as they continue the campaign of massacre & destruction,” tweeted Amrullah Saleh, a former intelligence chief who is now Ghani’s running mate in a presidential election scheduled for September. Saleh said the Taliban “should agree to direct & focused negotiations with the Afghan government.”

Several other delegates, reached by phone in Kabul, said they still planned to attend any talks but complained of poor management by Ghani’s peace team and excessive demands by the Taliban. The Taliban insisted that any Afghan officials participate only as private individuals so as not to confer legitimacy on a government the insurgents call an American puppet regime.

On Wednesday, after the delegation was announced, the Taliban ridiculed it as far too large and poorly organized. In a statement, a Taliban spokesman said the group’s meetings with U.S. officials had been “orderly” and well planned, while the sprawling Afghan delegation seemed more like an “Afghan wedding or other party in Kabul.”

One delegate, a political activist named Mohammad Idrees Stanikzai, said the Taliban was trying to weed out delegates who were “vocal critics of their wrongdoings” during the five years of repressive Taliban rule from 1996 to 2001. He said many young Afghans want an “Islamic republic, not an Islamic emirate,” or religious government. “We will defend our rights, and we will ask them to join the system.”

The U.S.-led talks with Taliban officials, which began several months ago, have completed five rounds without any major progress. The insurgents’ priority is the withdrawal of all foreign troops, and until now the group has refused to meet formally with any Afghan officials, although it did interact with some Afghan leaders at a meeting in Moscow.

Many Afghans have expressed fears that U.S. haste to reach a deal with the Taliban would sacrifice their concerns about future political and social rights if the Taliban regains a measure of power. The main goal of the now-canceled intra-Afghan meeting was to express those concerns directly to the Taliban.

Sayed Salahuddin and Sharif Hassan in Kabul contributed to this report.