With thousands of desperate Afghans and foreigners massed at Kabul's airport in the hope of fleeing Afghanistan's new Taliban rulers, US President Joe Biden is expected to decide as soon as Tuesday on whether to extend an Aug 31 deadline to airlift Americans and their allies to safety.

Biden warned on Sunday that the evacuation was going to be "hard and painful" and a lot could still go wrong. US troops might stay beyond Biden's Aug 31 deadline to...