The head of the United Nation's nuclear watchdog, Mohamed ElBaradei, has called for a new global system to prevent the spread of nuclear weapons.
ElBaradei said countries felt a need for nuclear deterrence
He said that after the Cold War and the 11 September attacks on the US, many countries felt they could only achieve security through nuclear deterrent.
He also raised the threat of "extremist terrorists" who sought nuclear weapons.
Mr ElBaradei said the crisis over North Korea's nuclear arms sent "the worst signal" to potential proliferators.
Addressing a seminar of the Council on Foreign Relations in New York, Mr ElBaradei said that a first step towards better international control could be a global moratorium on the right of any country to develop plutonium and highly-enriched uranium.
The two substances can be used to manufacture nuclear bombs.
Mr ElBaradei said North Korea had shown that a country which protected its weapons programmes and accelerated them could force powerful countries to the negotiating table.
"If you want to protect yourself, accelerate yourself ...then people will sit around the table with you," he said
He said Iran had the "know how" to enrich uranium, although there was no proof it had done so to military levels.
But, he said, the issue would only be brought to a close when "we can say Iran's programme is dedicated exclusively for peaceful purposes, and we are not there yet."
Mr ElBaradei said there were 100 facilities in 40 countries using highly enriched uranium, adding that it was time for a nuclear "clean-up".