SYDNEY, Nov 8: The world must take immediate action against the real threat of nuclear terrorism to prevent a September 11-style outrage, the head of the UN's atomic energy watchdog agency warned on Monday.

Calling it a "race against time", International Atomic Energy Agency (IAEA) chief Mohamed ElBaradei said past assumptions about how to control the spread of nuclear materials must be radically revised.

ElBaradei said his agency had never assumed until the attacks of September 11 that terrorists would deliberately use nuclear or radiological weapons or be willing to lose their own lives.

Those attacks and the growth of an illicit market in radioactive materials had left previous assumptions about nuclear security completely out of date, he told a two-day conference on curbing proliferation.

"We need to take preventive measures before a nuclear or radiological emergency. We should not wait to see the kind of situation like 9/11 or Chernobyl," he said.

"The danger exists everywhere. It's real, it's current and it's everywhere. We have to cross our fingers that nothing will happen."

Australian Foreign Minister Alexander Downer said preventive measures should get greater consideration considering the international outcry that would result from any radiological attack.

"There would be a sense of global pandemonium," he said.

The level of security surrounding nuclear facilities was inadequate in some places, he added.

Downer said the most likely kind of attack was some kind of radiological "dirty bomb" which would contaminate a large area rather than terrorists building or stealing a nuclear bomb and detonating it.

ElBaradei said key themes emerging at the conference were preventing the theft of nuclear material and making sure such material was used peacefully.

Referring to Iran's suspected nuclear weapons program, ElBaradei said a country with enriched uranium or plutonium was a "latent nuclear weapons state" and multinational control of the nuclear fuel cycle for civilian reactors might be needed.

A country with enriched uranium or plutonium could manufacture a weapon within months, he said.

"We do not want to see ourselves in the next 10, 20 years with 40, 50 countries sitting on plutonium or highly enriched uranium. I think the security margin that provides is very close for comfort," he said.

"In the post-9/11 environment, to see countries enriching uranium and the number of countries enriching uranium expanding all the time is a matter of enormous concern."

The agency's work on suspected nuclear weapons programs in Libya and Iran had revealed an extensive black market for radioactive materials, with around 630 confirmed incidents of trafficking in nuclear or other radioactive materials since 1993, he said.

This illicit market "clearly thrived on demand", he said.

"The relative ease with which a multinational illicit network could be set up and operated demonstrates clearly the inadequacy of the present export control system," he said.

More than two dozen companies and individuals were involved and in most cases the market carried on without the knowledge of their governments.

"The technical barriers to mastering the essential steps of uranium enrichment - and to designing weapons - have eroded over time," he said.

Downer pointed out that the September 11 hijackers had considered targeting US nuclear facilities.

He described as a "wake-up call" the uncovering of the network of Dr Abdul Qadeer Khan. "Khan's network was peddling the know-how and materials to make some of the most destructive weapons known," Mr Downer said in a prepared speech to the conference, made available in advance.

"The revelations of the Khan network are a reminder that in the post-September 11 world, there is no room for complacency," he said. "We must act decisively against the threat of nuclear proliferation."-AFP