Forty-seven world leaders are gathered in Washington for the biggest summit hosted by an American leader since the UN was founded in San Francisco in 1945. President Obama says he wants specific rules to halt the spread of nuclear materials, not what he called, "just some vague, gauzy statement.” Daniel Stone is senior reporter on national politics for Newsweek magazine.
Segment image: President Barack Obama meets with King Abdullah II of Jordan at the Nuclear Security Summit. Official White House Photo: Lawrence Jackson
