As the head of the International Commission on Nuclear Non-proliferation and Disarmament, Mr Evans placed the nuclear threat among the three biggest issues facing the globe, alongside climate change and the economic meltdown.

"This isn't the stuff of science fiction and fantasy," the former foreign affairs minister said yesterday after addressing the federal Parliament's treaties committee in Canberra. "It's really very fragile, this whole system."

The biggest concerns were nuclear powers such as North Korea and Iran using weapons deliberately; proliferation to Egypt, Turkey and Saudi Arabia and increased access to materials if nuclear energy became more widely embraced.

That poorly secured weapons could fall into terrorists' hands was also a threat. After "a decade of sleepwalking", the efforts Australia was making to re-engage with the global push towards disarmament and non-proliferation was timely, Mr Evans said.

A new nuclear non-proliferation treaty was due to be negotiated in 2010. Significant gains could be made if Russia and the United States agreed to reduce their arsenal, he said. Between them, the two nations hold about 90 per cent of the world's warheads, far more than a deterrent required, he said.

Last month, Mr Evans met the US Vice-President, Joe Biden, and the National Security Adviser, Jim Jones, to outline a plan for reducing the nuclear threat. The good intentions signalled by the US President, Barack Obama, were energising, he said.

According to Mr Evans, there was a 5 to 10 per cent risk of a nuclear disaster in a capital city in the next 10 years. The efforts of middle powers such as Australia and Japan could be formidable, he said. Israel, India, Pakistan and North Korea operate outside the non-proliferation treaty.