WASHINGTON - APRIL 12: U.S. President Barack Obama (L) welcomes Mohamed bin Zayed Al Nahyan, Crown Prince of Abu Dhabi and Deputy Supreme Commander of the United Arab Emirates Armed Forces, to the start of the Nuclear Security Summit at the Washington Convention Center April 12, 2010 in Washington, DC. Forty-seven delegations from around the world have converged on the United States' capital to discuss nuclear security. (Photo by Chip Somodevilla/Getty Images)
