media caption'Chaos was inevitable', Joe Biden told ABC News.

US President Joe Biden has said US troops may stay in Afghanistan beyond his withdrawal deadline, as armed Taliban fighters kept desperate evacuees from reaching Kabul's airport.

Mr Biden wants US troops out by the end of this month, but up to 15,000 US citizens are stranded in the country.

The US president told ABC News the turmoil in Kabul was unavoidable.

Foreign governments are ramping up the airlift of Western citizens and Afghans who worked with them.

About 4,500 US troops are in temporary control of Karzai International Airport in the nation's capital, but Taliban fighters and checkpoints ring the perimeter.

US nationals told the BBC's US partner CBS News they have been unable to enter the airport for scheduled evacuation flights.

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In a press conference earlier on Wednesday, US Defence Secretary Lloyd Austin was asked if the American military had the capability to rescue the stranded Americans.

"We don't have the capability to go out and collect large numbers of people," he replied.

Mr Biden, a Democrat, told ABC the US would stay to get all Americans out of Afghanistan, even if it meant remaining beyond the 31 August deadline for a complete withdrawal.

"If there's American citizens left, we're gonna stay to get them all out," he said.

The US president said between 10,000 and 15,000 Americans needed to be evacuated, along with 50,000 to 65,000 Afghans such as former translators for the American military.

The Pentagon told reporters 5,000 people have already been evacuated from Kabul and they aim to expand the airlift to 9,000 people a day. A Western official told Reuters news agency those evacuated so far were diplomats, security staff, aid workers and Afghans.

US Deputy Secretary of State Wendy Sherman said American officials have told the Taliban that Washington expects them to allow all American citizens, all third-country nationals, and all Afghans who want to leave to do so, safely and without harassment.

Asked by ABC if he would acknowledge any mistakes in the chaotic withdrawal, Mr Biden said: "No."

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He added: "The idea that somehow there's a way to have gotten out without chaos ensuing, I don't know how that happens."

Mr Biden was also asked about images that went viral this week of Afghans falling from an American military plane as it gained altitude over Kabul.

The US president grew defensive, saying: "That was four days ago, five days ago!"

Mr Biden was also pressed on his assessment only last month that a Taliban takeover of the country was "highly unlikely".

He said intelligence reports had suggested such a scenario was more likely by the end of this year.

"You didn't put a timeline out when you said 'highly unlikely'," said interviewer George Stephanopoulos. "You just said flat out it's 'highly unlikely that the Taliban would take over.'"

"Yeah," replied Mr Biden, who also assured Americans back in April that the US withdrawal would be safe and orderly.

In Wednesday's interview, the US president again blamed the Afghan government and its military for the Taliban's lightning conquest of the country.

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Intelligence sources tell the BBC that Mr Biden had well understood the risks of his withdrawal, but he was strident in his decision to get out this year.

In the end, he was "functioning as his own principal analyst", said Paul Pillar, a former CIA officer now at Georgetown University.

"The Taliban was eventually going to prevail," Mr Pillar said. "But the speed or pace, or when something is going to happen, is essentially unpredictable."

"Was this an intelligence failure? My guess is probably not," he added.

On Wednesday, the International Monetary Fund suspended Afghanistan's access to $440m (£320m) in monetary reserves – a move pushed for by the US Treasury to prevent funds falling into Taliban hands.

Deposed Afghan President Ashraf Ghani, who fled Afghanistan as Taliban forces swept into Kabul on Sunday, meanwhile said he had merely been following the advice of government officials.

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In a video streamed on Facebook, Mr Ghani – currently in exile in the United Arab Emirates – denied Russian claims that he had made his getaway in a helicopter full of cash.

At least one person was killed during anti-Taliban protests on Wednesday in Jalalabad, about 150km (90 miles) east of Kabul.

Taliban fighters reportedly attacked demonstrators who were attempting to lower the militant group's flag and replaced it with the Afghan national tricolor.