Obama rallies world leaders at nuclear summit

US President Barack Obama rallied world leaders at an unprecedented summit on preventing nuclear terrorism against the backdrop of a mounting US-led drive to tighten sanctions on nuclear-defiant Iran.

Hosting a 47-nation conference, Obama called for concerted global action to lock down loose nuclear materials, warning that if al-Qaida acquired an atomic weapon it would be a “catastrophe for the world”.

“Two decades after the end of the Cold War, we face a cruel irony of history — the risk of a nuclear confrontation between nations has gone down, but the risk of a nuclear attack has gone up,” Obama said.