The US will continue to help people to leave Afghanistan after the 31 August deadline, Antony Blinken has said.

The secretary of state told a news conference on Wednesday that about 4,500 Americans, out of the 6,000 who wanted to leave Afghanistan when the airlift began on 14 August, have been evacuated so far.

Mr Blinken said that the US is “aggressively” reaching out to around 1,000 people – thought to be Americans – still in the country while 500 more have been contacted with instructions on how to catch evacuation flights from Kabul airport.

Despite maintaining that the US airlift will end on 31 August, Mr Blinken said it will continue to help any of its citizens, or Afghans who want to leave, to get out after this date.

“There is no deadline on our work to help any remaining American citizens who decide if they want to leave to do so along with the many Afghans who have stood by us over these many years and want to leave and have been unable to do so,” Mr Blinken said.

“That effort will continue every day past the 31st.”

The secretary of state emphasised that the Taliban has agreed, in public and in private, that people will be allowed to leave Afghanistan after the end of the month.

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He also said President Joe Biden had asked him for contingency plans in the event that the timeline needs to be adjusted.

Mr Blinken said: “It’s hard to overstate the complexity and dangers of this effort.”

Mr Biden earlier said the US is on track to finish its effort in the country by 31 August but refugee groups described a disorganised evacuation effort for Afghan allies that leaves the most desperate to risk beatings at Taliban checkpoints.

Some Afghans are reportedly being turned away from the Kabul airport by American forces controlling the gates, despite having approval for flights.

“It’s 100% up to the Afghans to take these risks and try to fight their way out,” said Sunil Varghese, policy director with the International Refugee Assistance Project.

“Those with young children and pregnant are willing to take those beatings to get out.”

His group is one of several working with the US government, and communicating with clients and colleagues on the ground, to get out those Afghans most in danger from the Taliban.

Those include Afghans who formerly worked with Americans, as well as journalists and women’s rights advocates.

Taliban leaders who took control of Afghanistan this month say they will not tolerate any extensions to the Tuesday deadline.

But Taliban spokesman Suhail Shaheen tweeted that “people with legal documents” will still be able to fly out via commercial flights after next Tuesday.