WASHINGTON (AP) — Secretary of State Antony Blinken says as many as 1,500 Americans in Afghanistan may still await evacuation, as concerns of a terror attack targeting Kabul’s airport grow in the airlift’s final days. New European warnings of an immediate threat Thursday came after a U.S. security alert, urging Americans to stay away from certain gates at the airport, the heart of a two-week evacuation effort. Blinken said 4,500 Americans have been flown out of the country ahead of President Joe Biden’s Tuesday deadline for withdrawing troops. Veterans groups and refugee organizations say countless Afghan allies at risk from the Taliban may be left behind when U.S. forces leave.