WASHINGTON (AP) — President Barack Obama authorized U.S. airstrikes in northern Iraq Thursday night, warning they would be launched if needed to defend Americans from advancing Islamic militants and protect civilians under siege. His announcement threatened a renewal of U.S. military involvement in the country’s long sectarian war.

In a televised late-night statement from the White House, Obama said American military planes already had carried out airdrops of humanitarian aid to tens of thousands of Iraqi religious minorities surrounded by militants and desperately in need of food and water.