President Obama Hosts World Leaders At Nuclear Security Summit

WASHINGTON - APRIL 13: U.S. President Barack Obama (C) talks with German Chancellor Angela Merkel and Prime Minister of Singapore Lee Hsien Loong (R) while joining other world political leaders for the opening plenary session of the Nuclear Security Summit at the Washington Convention Center April 13, 2010 in Washington, DC. Forty-seven countries have gathered at the invitation of the U.S. government to talk about nuclear safety and how to make dangerous materials less accessible to terrorists. (Photo by Chip Somodevilla/Getty Images)