Make breaking, leaving nuke treaty harder, US says

GENEVA (Reuters) - States that break or leave the treaty preventing the spread of nuclear weapons should face tougher sanctions than at present, the top U.S. nonproliferation official said on Wednesday.

Susan Burk said the world now had a real opportunity to strengthen the regime enshrined in the Nuclear Nonproliferation Treaty (NPT), and President Barack Obama's administration was determined to make an ambitious effort to do so.