United States President Joe Biden on Friday claimed that the evacuation operation from Afghanistan was “one of the largest, most difficult airlifts in history”.

In a press briefing, Biden reiterated he would evacuate all American citizens from Afghanistan, adding however, that he could not promise what the “final outcome” of the operation would be. He also said the US was “committed” to rescuing Afghans who had worked alongside the country’s troops during their 20-year presence in the country.

“Let me be clear, any American who wants to come home, we will get you home,” Biden said. “But make no mistake: This evacuation mission is dangerous. It involves risks to our armed forces, and it is being conducted under difficult circumstances.”

He added that about 13,000 people had been evacuated by US military aircraft since August 14, while 5,700 were evacuated on Thursday alone.

Biden’s comments came two days after he said that the country’s troops would stay in Afghanistan until every American is evacuated. On Wednesday, he had said the troops would stay even beyond its August 31 deadline for this purpose, if needed.

On Friday, the US president also sought to respond to criticism for not planning the evacuation of Americans and Afghan allies from the country sooner and misjudging the pace at which the Taliban would take over.

“There’ll be plenty of time to criticise and second guess when this operation is over,” Biden said, adding that “the buck stops with me.”

Responding to a reporter’s question, the president said that the US military was not looking to expand its existing security perimeter beyond the Kabul airport. However, in his brief before taking questions, Biden had said that on Thursday, the military helicopters flew beyond the airport to rescue 169 Americans who had jumped over the facility’s walls.

He also said that US officials were in constant contact with the Taliban, adding that an attack on the forces or disruption of evacuation operations would “be met with a swift and forceful response”.

Meanwhile, flights evacuating Americans and others were stopped for several hours on Friday because of crowding at the US airbase in Qatar. However, they resumed in the afternoon, including to Bahrain, AP reported.

On August 15, the Taliban took over the presidential palace in Kabul after President Ashraf Ghani fled to the United Arab Emirates. The fall of Kabul was followed by a swift takeover by the Taliban. The Taliban’s clashes with Afghan forces had escalated in recent weeks as foreign troops were preparing to withdraw from the country by the end of August.