WARSAW, Poland—Poland and Belgium ended their evacuations from Afghanistan, but other European nations vowed Wednesday to press on for as long as possible, as the clock ticks down on a dramatic airlift of people fleeing Taliban rule ahead of a full American withdrawal. President Joe Biden said he will stick to his Aug. 31 deadline for completing the U.S. pullout. European allies pressed for more time but, as a practical matter, will need to end their evacuations before the last American troops leave. Several countries have not said when they plan to end their operations. The Taliban wrested back control of Afghanistan nearly 20 years after they were ousted in a U.S.-led invasion following the 9/11 attacks, which al-Qaida orchestrated while being sheltered by the group. Their return to power has pushed many Afghans to flee, fearing reprisals and a possible return to their brutal rule. Late Wednesday, the U.S. …