President Obama Hosts World Leaders At Nuclear Security Summit

WASHINGTON - APRIL 13: U.S. President Barack Obama (L) speaks during the opening plenary session as Argentinia Presiden Cristina Fernandez de Kirchner (R) and U.S. Vice President Joseph Biden (2nd R) listen during the Nuclear Security Summit at the Washington Convention Center April 13, 2010 in Washington, DC. Delegates from forty-seven countries have gathered at the invitation of the U.S. government to talk about nuclear security and how to make dangerous materials less accessible to terrorists. (Photo by Andrew Harrer-Pool/Getty Images)