U.S. United Nations Ambassador Samantha Power addresses the 2015 American Israel Public Affairs Committee (AIPAC) Policy Conference in Washington, Monday, March 2, 2015. (AP Photo/Cliff Owen)
Samantha Power, U.S. Ambassador to the U.N., speaks during a news conference after a private U.N. Security Council meeting on the Ukraine, Friday, Feb. 28, 2014, at United Nation headquarters. (AP Photo/Bebeto Matthews)
**FILE** U.S. United Nations Ambassador Samantha Power speaks about Syria on Sept. 6, 2013, at the Center for American Progress in Washington. (Associated Press)