Representatives of 53 countries present at the two-day summit ended the talks with a pledge to secure nuclear material against potential use by terrorists, as well as to work towards non-proliferation.

US President Barack Obama told leaders that steps to improve nuclear security had already made the world a safer place, but warned that the threat persisted that terrorists would one day build and explode a crude atomic bomb.

"The threat remains," Obama said. "There are still too many bad actors in search of these dangerous materials, and these dangerous materials are still vulnerable in too many places."

"It would not take much, just a handful or so of these materials, to kill hundreds of thousands of innocent people."

The summit's final communiqué called for "a safer world for all," agreeing that nuclear terrorism was "one of the most challenging threats to international security."

Details thin, pledges non-binding

However, while the statement was rich with general commitments, there was little in the way of specifics on how to reduce the risk of atomic materials falling into the wrong hands. The pledges contained in the communiqué were also left non-binding.

The long and vaguely worded document offered nothing in the shape of measurable targets and did not single out any state for criticism.

Although the meeting was only intended to deal with the safeguarding of nuclear material, Japanese Prime Minister Yoshihiko Noda ignored protocol to issue a strong demand that North Korea cancel a rocket launch - viewed by the West as a long-rage nuclear missile test - planned for next month.

Nuclear power Pyongyang remained defiant, vowing on Tuesday to carry out the "peaceful" launch of what it claims is a satellite.

rc/dfm (dpa/Reuters)