Obama Opens Nuclear Summit

Barack Obama has opened a meeting of the world's major nuclear powers in Washington, in what the US president has heralded as the first concerted effort to confront the threat of nuclear material falling into the wrong hands. Monday's first day of talks was dominated by two developments – an apparent agreement for the US and China to work together on sanctions against Iran; and an announcement that Ukraine would surrender its stockpile of weapons-grade uranium. Attending the summit are leaders and delegates from the five major nuclear powers and 42 others, in what is the largest international meeting hosted by a US president in more than 60 years. Notable exclusions from the gathering include Iran, North Korea and Syria.