As Western nations struggled to ramp up the pace of evacuations from Afghanistan, U.S. President Joe Biden confronted criticism over the withdrawal of U.S. troops and the Taliban's swift takeover of the country.

"I have seen no question of our credibility from our allies," Biden told reporters after making a speech from the White House. "As a matter of fact, the exact opposite I've got... we're acting with dispatch, we're acting, committing to what we said we would do."

Thousands of desperate Afghans clutching papers, children and a bit of belongings thronged Kabul airport where gun-toting Taliban members outside urged those without travel documents to go home. In and around the airport, at least 12 people have been killed since Sunday, NATO and Taliban officials said.

U.S. evacuation flights from Kabul's airport stopped for more than six hours on Friday while U.S. authorities looked for countries willing to accept people fleeing Afghanistan. The flights resumed later in the day.

In his remarks, Biden referred to the 169 Americans transported by the military. Department of Defense spokesman John Kirby later said the decision was made to use the helicopters on Thursday because the group was unable to get to the gate from a nearby hotel to the airport.

"The plan was simply (for them) to walk through the gate, but there was a large crowd established outside the Abbey gate, a crowd that not everybody had confidence in, in terms of their ability to walk through and so local commanders on the scene took the initiative and flew these helicopters out there to pick them up," Kirby said.

Biden insisted every American who wanted to would be evacuated, and that about 18,000 people had been airlifted out since July.

NATO Secretary-General Jens Stoltenberg described the situation outside Kabul airport as "very dire and difficult," as several member countries pressed for evacuations to continue beyond an August 31 U.S. deadline.

Biden has not backed off that deadline, despite calls – internationally and at home from his fellow Democrats as well as opposition Republicans – to keep troops in Afghanistan as long as necessary to bring home every American.

Biden said he could not predict what the final outcome would be in Afghanistan, where the United States and allies have waged a 20-year war. But he promised to work with other countries to set "harsh conditions" for any cooperation or recognition of the Taliban, based on their human rights record.

On Saturday, a Taliban official told Reuters on condition of anonymity that the group is aiming to unveil a new governing framework for Afghanistan in the next few weeks.

The framework would not be a democracy by Western definition, but "It will protect everyone's rights," the official added.

The Taliban have sought to present a more moderate face since last week's lightning takeover, despite their previous history of ruling with an iron fist from 1996 to 2001 before being toppled by U.S.-led forces for sheltering al Qaeda militants behind the September 11 attacks.

The official added that the group will also be accountable for its actions and will investigate reports of reprisals and atrocities carried out by members, Reuters reports.

"We have heard of some cases of atrocities and crimes against civilians," the official said. "We can understand the panic, stress and anxiety. People think we will not be accountable, but that will not be the case." 

"If Talibs (members) are doing these law and order problems, they will be investigated." 

(With input from Reuters)