US Secretary of State Antony Blinken said Tuesday that the Taliban had reiterated a pledge to allow Afghans to freely depart Afghanistan following his meeting with Qatari officials on accelerating evacuations.

US President Joe Biden has faced mounting pressure amid reports that several hundred people, also including Americans, had been prevented for a week from flying out of an airport in northern Afghanistan.

The Taliban told the United States that "they will let people with travel documents freely depart," Blinken told a news conference in Doha where he and Defense Secretary Lloyd Austin met their Qatari opposite numbers.

"We will hold them to that," he added.

Qatar said that Kabul airport, largely closed since the conclusion of Washington's chaotic withdrawal from the country at the end of August, would hopefully reopen soon, potentially opening an important corridor for Afghans seeking to leave.

"The entire international community is looking to the Taliban to uphold that commitment," Blinken said, referring to a UN Security Council resolution that urged safe passage.

Biden's senior cabinet members had dinner on arrival Monday with Qatar's ruler Emir Sheikh Tamim bin Hamad Al-Thani where they expressed Washington's thanks to Doha for its assistance with the Afghanistan airlift.

'Extraordinary support'

Qatar was the transit point for nearly half of the more than 120,000 people evacuated from Afghanistan in the final days of the 20-year US war as the Taliban took over.

Doha is the Taliban's international diplomatic base although Blinken's aides said he has no plans to meet them as Washington instead waits to judge the group's actions in power to determine the level of engagement.

The United States on Monday facilitated the evacuation of four Americans from the same family by land out of Afghanistan, the first departures arranged by Washington since the military pullout.

A State Department official said the Taliban were aware of the operation and did not interfere.

But non-governmental organisations say that some 600 to 1,300 people -- including girls and US citizens -- are stuck at the airport in the northern city of Mazar-i-Sharif.

Marina LeGree, the founder and executive director of a small American non-governmental organisation active in Afghanistan, told AFP that the Taliban are not letting anyone through.

Blinken said that the Taliban had not blocked people with valid travel documents but that not all passengers on charter flights had papers, denying there was a "hostage-like situation" in Mazar-i-Sharif.

He said there were inevitable obstacles to charter flights as the United States does not have personnel on the ground.

"We don't have the means to verify the accuracy of manifests, the identity of passengers aboard these planes, aviation security protocols, or where they plan to land -- among other issues. These are real concerns," he said.

"We are engaging as we speak to resolve these issues," he said.

US officials say they no longer control the airspace in Afghanistan and that the main airport in Kabul, which the US military seized in August for evacuations, is in disrepair.

Qatari technical teams have deployed to Kabul to assess the viability of the airport and begin to prepare it for a return to operation to allow evacuations and the arrival of badly needed humanitarian supplies.

Blinken in his meeting with the Gulf state's ruler hailed "Qatar's extraordinary support in facilitating the safe transit of US citizens, our partners, and other Afghans at-risk," the State Department said.

Austin acknowledged that the withdrawal created obstacles but said the United States was committed to stopping threats from Afghanistan.

"There is no question it (the withdrawal) will make it more difficult to identify and engage threats that emanate from the region," Austin said.