President Obama Hosts World Leaders At Nuclear Security Summit

WASHINGTON - APRIL 13: U.S. President Barack Obama (C) greets President of Kazakhstan Nursultan Nazarbayev (L) as King Abdullah II (R) of Jordan, and upper row (L-R), President of Ukraine Viktor Yanukovych, President of South Africa Jacob Zuma, and President of Russia Dmitry Medvedev look on during the group photo session of the Nuclear Security Summit 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 Alex Wong/Getty Images)