Biden warned on Sunday that the evacuation was going to be "hard and painful" and much could still go wrong. U.S. troops might stay beyond an Aug. 31 deadline to oversee the evacuation, he said.

On Monday, an administration official told Reuters that Biden would decide within 24 hours whether to extend the timeline to give the Pentagon time to prepare.

Beyond the need to remove thousands of Americans, citizens of allied countries and Afghans who worked with U.S. forces, Department of Defense officials said it would still take days to fly out the 6,000 troops deployed to secure and run the airlift.

Some Biden advisers were arguing against extending the self-imposed deadline for security reasons. Biden could signal his intentions at a virtual meeting of the Group of Seven wealthy nations on Tuesday.

Two U.S. officials had said the expectation was that the United States would continue evacuations past Aug. 31. A senior State Department official told reporters the country's commitment to at-risk Afghans "doesn't end on Aug. 31."

Later on Monday, Democratic U.S. Representative Adam Schiff, chairman of the House of Representatives Intelligence Committee, told reporters after a briefing on Afghanistan by intelligence officials that he did not believe the evacuation could be completed in the eight remaining days.

"I think it's possible but I think it's very unlikely given the number of Americans who still need to be evacuated," Schiff said.

A Taliban official said foreign forces had not sought an extension and it would not be granted if they had. Washington said negotiations were continuing.

White House national security adviser Jake Sullivan said the United States was in daily talks with the Taliban and making "enormous progress" in evacuating Americans and others.

Between 3 a.m. and 3 p.m. local time on Monday, some 10,900 people were evacuated from Kabul, meaning the United States had facilitated the removal of 48,000 people since Aug. 14.

U.S. defense officials had told Reuters that almost everything would have to go perfectly to extricate every American citizen by Aug. 31, given concerns about reaching the airport, terrorist attacks and complicated processing times.

State Department spokesman Ned Price told reporters the United States had discussed future control of the airport with the Taliban, as well as with U.S. partners and allies.

Afghans board a U.S. Air Force C-17 Globemaster III transport plane during an evacuation at Hamid Karzai International Airport, Afghanistan, August 22, 2021. U.S. Air Force/Handout via REUTERS U.S. Marines and Norwegian coalition forces assist with security at an Evacuation Control Checkpoint ensuring evacuees are processed safely during an evacuation at Hamid Karzai International Airport, Kabul, Afghanistan, August 20, 2021.   U.S. Marine Corps/Staff Sgt. Victor Mancilla A still image taken from video shows crowds of people near the airport in Kabul, August 23, 2021. ASVAKA NEWS via REUTERS 1/8

U.S. Marines and Norwegian coalition forces assist with security at an Evacuation Control Checkpoint ensuring evacuees are processed safely during an evacuation at Hamid Karzai International Airport, Kabul, Afghanistan, August 20, 2021. U.S. Marine Corps/Staff Sgt. Victor Mancilla 'DOES IT STILL HURT? YES'

The Taliban's swift takeover and ensuing chaos in Afghanistan have roiled U.S. politics, with opposition Republicans piling criticism on Biden for the withdrawal, which was initiated by his Republican predecessor, Donald Trump. Biden's opinion poll numbers have slipped.

Biden's fellow Democrats who control Congress have promised to investigate what went wrong in Afghanistan within the past weeks and throughout the 20-year conflict, America's longest war.

For its part, the powerful U.S. military has been grappling with the collapse of U.S.-backed Afghan forces after 20 years of training. "Was it worth it? Yes. Does it still hurt? Yes," General David Berger, the commandant of the Marine Corps, wrote in a memo to Marines.

The difficulties at the airport were underlined on Monday with a firefight between Afghan guards and unidentified gunmen. German and U.S. forces were also involved, the Germany military said.

A local Taliban militant, speaking to a large crowd in Kabul, urged Afghans to remain.

"Where has our honor gone to? Where has our dignity gone to?" the unidentified militant said. "We will not let the Americans continue to be here. They will have to leave this place. Whether it is a gun or a pen, we will fight to our last breath."

WORKING WITH ALLIES

The Taliban seized power last week as the United States and its allies withdrew troops after the war launched after the Sept. 11, 2001, attacks.

Panicked Afghans and foreigners have thronged the airport since, clamoring to catch any flight out. Many fear reprisals and a return to a harsh version of Islamic law the Taliban enforced while in power from 1996 to 2001.

Twenty people have been killed, most in shootings and stampedes, as international forces try to bring order. One member of the Afghan forces was killed and several wounded in Monday's clash, the U.S. military said.

A British government spokesperson said British evacuations could not continue once U.S. troops leave. French Foreign Minister Jean-Yves Le Drian also said more time was needed.

German Foreign Minister Heiko Maas said the virtual G7 summit must agree on whether to extend the deadline and how to improve access to the airport.

The airport chaos also disrupted aid shipments. The World Health Organization said tons of medical supplies were stuck because Kabul airport was closed to commercial flights.

Leaders of the Taliban, who have sought to show a more moderate face since capturing Kabul, have begun talks on forming a government, while their forces focus on the last pockets of opposition.