Countries with nuclear plants must carry out a "thorough and transparent risk assessment" of all reactors within 18 months.
International Atomic Energy Agency (IAEA) director general Yukiya Amano said an urgent international response was needed to help address public safety concerns caused by Japan's atomic crisis.
"We need to respond urgently to the public anxiety," Amano said at an international meeting on strengthening nuclear safety following the Fukushima disaster in Japan.
"An international response is essential."
The crisis at the Fukushima Daiichi plant has been described as the world's worst nuclear disaster since Chernobyl.
IAEA officials are reviewing safety standards at nuclear plants across the world and will report back to Amano in 12 months on how to strengthen them.
"Nuclear safety will remain the responsibility of states," he said, adding that IAEA will play a leading role in shaping improvements.
See E&T's feature on Germany's decision to decommission its nuclear power plants