`` There is an increased threat stream , '' says one senior U.S. official . The United States has been working with the Saudis, who have a long history of supporting extremist groups in Syria and elsewhere, to try to prevent Iran from getting its hands on nuclear weapons. Yemeni authorities are on high alert , expecting `` imminent retaliatory attacks , '' an official says .
`` There is an increased threat stream , '' says one senior U.S. official . At least 65 suspected al Qaeda members were killed in a Yemeni-U.S. joint operation . Yemeni authorities are on high alert , expecting `` imminent retaliatory attacks , '' an official says .