US forces are in the final phase of leaving Kabul, ending two decades of involvement in Afghanistan, and just over 1,000 civilians at the airport remain to be flown out before troops withdraw, a Western security official said on Sunday.

The country's new Taliban rulers are prepared to take control of the airport, said an official from the hardline Islamist movement that has swept across Afghanistan, crushing the US-backed government.

The Western security official, who asked not to be...