Secure material top concern

WASHINGTON - As world leaders gathered for the Nuclear Security Summit, experts warned that the threat from nuclear terrorism remains real and recommended ways to effectively secure nuclear material.

Robert Gallucci, a non-proliferation expert and former US ambassador, described the threat as "not only possible and plausible but probable over time," during a conference titled "Next Generation Nuclear Security: Meeting the Global Challenge" on Monday.

"The global risk from nuclear weapons and nuclear terrorists loom large," said Gallucci, now president of The John D. and Catherine T. MacArthur Foundation.