Day 1 of the Nuclear Security Summit (14 images)

Leaders of about four dozen nations and non-government organizations were called to Washington to discuss security of nuclear materials.

U.S. President Barack Obama convened the high-profile meeting to look into what he called the most severe security issue for the United States -- the possibility that a terror group such as al-Qaida obtained nuclear materials and used them in an attack on U.S. interests.

Updated: April 12, 2010 at 9:33 AM
1 of 14
President Barack Obama and Secretary of state Hillary Clinton walk from the White House to the Blair House to participate in bilateral meetings April 11, 2010 in Washington, DC. UPI/Olivier Douliery/Pool
| License Photo