The United States aimed to complete evacuations from Taliban-controlled Afghanistan by a 31 August withdrawal deadline - as calls grow from allies to extend it.

The Pentagon said it was not yet at the point to seek a change, though Britain, France and Germany will step up the pressure at a virtual G7 summit for extension in the deadline.

The Taliban told the BBC that any extension would violate an agreed deal.

Tens of thousands have been evacuated, but others seeking to flee remain crammed in or near Kabul airport.

US President Joe Biden is expected to decide within the next 24 hours on whether to extend the timeline for withdrawal. An unnamed official told a British news agency that the decision would be made in order to give the Pentagon time to prepare.

At Kabul airport, dozens crowded around a BBC reporter, desperately flashing documents to try to get on to flights they had not been given permission to board.

The US military shuttled thousands of more people through the Kabul airport during the last 24 hours, a White House official said as Washington attempts to complete a daring airlift by an August 31 deadline for troops to leave Afghanistan.

In the 12 hours up until 3:00 pm Monday (1900 GMT), about 10,900 people were evacuated from Hamid Karzai International Airport, the official said, updating figures given earlier in the day at the Pentagon. 

The number of people relocated from Afghanistan since July on US flights hit 53,000, with 48,000 of those since the intense airlift operations started on August 14 as the Taliban moved into Kabul.

Earlier, Pentagon spokesman John Kirby said those evacuated included "several thousand" US citizens, and thousands of Afghans who worked for US forces, who had applied for or received special immigrant visas, and Afghans seen as at risk to Taliban attacks for their work in non-governmental organizations, the media, and other jobs.

Kirby said the focus remains on getting US evacuation operations done by the August 31 deadline that President Joe Biden has set for completing the US withdrawal from Afghanistan. 

That would require withdrawing the 5,800 US troops who have essentially run airport operations and maintained security since August 14, as well as large amounts of equipment brought in to support their mission.

German, British and French officials said Monday that evacuations on their part could continue after August 31, and said they want the US force to stay in place to help the international airlift.

Leaders of the G7 group of wealthy nations will meet virtually on Afghanistan on Tuesday.

"Whether or not the US can be persuaded to stay is a matter for the prime minister (Boris Johnson) tomorrow in the G7 meeting," British armed forces minister James Heappey told Sky News.

Britain currently chairs the G7, also comprising Canada, France, Germany, Italy, Japan and the United States.

Kirby did not categorically rule out Washington extending the deadline, although the Taliban have said they will hold the United States to it.

For the United States, Kirby said, "The goal is to get as many people out as fast as possible."

"The focus is on trying to do this as best we can, by the end of the month," he said.

At the White House, National Security Advisor Jake Sullivan deferred questions on extending the US pullout deadline to the G7 talks on Tuesday, saying the White House is taking the situation "day by day."

He said Biden had already spoke with Johnson on Monday.

"We remain in close touch with allies and partners to coordinate the evacuation of their own citizens and their priority personnel," Sullivan said.

He said that there is enough time to evacuate all the US citizens in the country who have sought to leave.

"We believe that we have time between now and the 31st to get out any American who wants to get out," he said.–Agencies