Joe Biden says the “hard and painful” airlift of Americans and tens of thousands of others from Afghanistan’s capital is accelerating, but would not rule out extending it beyond the August 31 deadline he set before the Taliban’s swift takeover.

A week after the Taliban completed their victory by capturing Kabul, the US president defended his decision to end the war and insisted that getting all Americans out of the country would have been difficult in the best of circumstances.

Critics have condemned him for waiting too long to begin organising an evacuation amid the fear and panic set off by the Afghan government’s sudden collapse.

“The evacuation of thousands of people from Kabul is going to be hard and painful, no matter when it started, when we began,” Mr Biden said.

“It would have been true if we’d started a month ago, or a month from now. There is no way to evacuate this many people without pain and loss of heartbreaking images you see on television.”

But there were signs of progress: over the 24 hours to Monday morning, 28 US military flights evacuated about 10,400 people from Kabul, according to a White House official.

In addition, 61 coalition aircraft evacuated approximately 5,900 people.

Mr Biden said military discussions are under way on potentially extending the airlift beyond his August 31 deadline. “Our hope is we will not have to extend, but there are discussions,” he added, suggesting the possibility that the Taliban will be consulted.

Since August 14, the US has evacuated and facilitated the evacuation of approximately 37,000 people. Since the end of July, the figure is 42,000, the White House official said.

“We see no reason why this tempo will not be kept up,” Mr Biden said from the White House. The US military says it has the capacity to fly 5,000-9,000 people out of Kabul per day.

Mr Biden said US forces have improved access to the airport for Americans and others seeking to get on flights. He suggested that the perimeter had been extended, widening a “safe zone”.

“What I’m not going to do is talk about the tactical changes we’re making to make sure we maintain as much security as we can,” he said.

“We have constantly, how can I say it, increased rational access to the airport, where more folk can get there more safely. It’s still a dangerous operation but I don’t want to go into the detail of how we’re doing that.”

Later he added: “We’ve discussed a lot with the Taliban. They’ve been co-operative in extending some of the perimeter.”

He said groups of Americans in Kabul are being moved more efficiently and safely to the airport, but did not provide details.

“Any American who wants to get home will get home,” he said.

Earlier on Sunday, administration officials said the US military is considering “creative ways” to get Americans and others into Kabul airport for evacuation, and the Pentagon on Sunday ordered six US commercial airlines to help move evacuees from temporary sites outside Afghanistan

Mr Biden said no Afghan evacuees are being flown directly to the US from Afghanistan without screening. He said they are being screened in third countries.

The president and his senior aides have repeatedly cited concern that extremist groups in Afghanistan will attempt to exploit the chaos around the airport.

“The threat is real, it is acute, it is persistent and something we’re focused with every tool in our arsenal,” said national security adviser Jake Sullivan.

The Biden administration has given no firm estimate of the number of Americans seeking to leave Afghanistan. Some have put the total between 10,000 and 15.000. Mr Sullivan on Sunday put it at “several thousand”.