The US military has begun its final pullout from Afghanistan, on high alert for new terror strikes, as part of a frenzied airlift of Americans, Afghans, and others seeking to flee Taliban rule before the evacuation ends.

According to the Pentagon, the remains of 13 American troops killed in an airport attack Thursday by members of the Islamic State group's Afghanistan affiliate, known as ISIS-K, were on their way to the United States.

The US President Joe Biden said on Tuesday that the US was on track to end its two-decade military presence in Afghanistan by his August 31 deadline.

However, the president stated at the White House that he had spoken with military leadership to ensure that they were prepared to “adjust that timetable, should that become necessary.”

“It is a tenuous situation,” Mr. Biden said.

“We are currently on pace to finish by Aug. 31,” he said. “The sooner we can finish, the better. Each day of operations brings added risk to our troops.”

However, he stated that a large part of the success of that effort was dependent on the Taliban continuing to cooperate with the operation and allowing access to the airport. He stated that the Taliban government's legitimacy in the eyes of the US and its allies had been dependent on the approach it now takes to uphold its international obligations, including making sure that Afghanistan will not become a base for terrorists once again.