The Summit was the largest gathering of heads of state called by a United States president since the 1945 United Nations Conference on International Organization . Delegations from forty-seven governments including the United States attended , thirty-eight of which were represented by heads of state or government . Delegations from the European Union , the International Atomic Energy Agency , and the United Nations also attended
United Nations Conference on International Organization
United Nations Conference on International Organization
2010 Nuclear Security Summit