"Obama, World Leaders Work to Stop Nuclear Spread"

"WASHINGTON -- President Barack Obama and presidents, prime ministers and other top officials from 47 countries start work Monday on a battle plan to keep nuclear weapons out of terrorist hands.

Confronting what he calls the "single biggest threat to U.S. security," Obama is looking for global help in his goal of ensuring all nuclear materials worldwide are secured from theft or diversion within four years.

On the eve of what would be the largest assembly of world leaders hosted by an American president since 1945 -- the San Francisco conference to found the United Nations -- Obama said nuclear materials in the hands of al-Qaida or another terrorist group "could change the security landscape in this country and around the world for years to come."

While sweeping or even bold new strategies were unlikely to emerge from the two-day gathering, Obama declared himself pleased with what he heard in warm-up meetings Sunday with the leaders of Kazakhstan, South Africa, India and Pakistan."

Steven R. Hurst and Anne Gearan report for the Associated Press April 12, 2010.