VIENNA, Feb 5: The UN nuclear agency chief said on Thursday Pakistan's top nuclear scientist was not working alone in creating an illicit network to sell nuclear technology to Libya, Iran and North Korea but had lots of help

"Dr (Abdul Qadeer) Khan was not working alone," International Atomic Energy Agency chief Mohamed ElBaradei told reporters, adding he had help from people in many countries. "Dr Khan is the tip of an iceberg for us."

Mr ElBaradei was speaking on the sidelines of a conference on nuclear non-proliferation at IAEA headquarters in Vienna.

"We need to follow this through. We need to know who was producing centrifuges" used for making weapons-grade uranium for atomic bombs.

"We have to make sure it will not be repeated," Mr ElBaradei said about the clandestine nuclear dealing.

He said Pakistan has been "quite cooperative so far" with the IAEA in trying to piece together what Mr ElBaradei called "a supermarket" of international smuggling of nuclear materials and information such as weapons blueprints the US has found in Libya.

But a Western diplomat close to the IAEA said the agency had not asked Pakistan if it could interview Khan. He said the political situation there was too sensitive. "The IAEA doesn't want Musharraf to fall. That would be the worst thing that could happen," he said.

He said the IAEA was able to gather information from Libya and Iran, where it is verifying compliance with international safeguards, about how Dr Khan and others helped them acquire nuclear technology.

"The IAEA talks to the Iranians and the Libyans and then puts facts together, with which it confronts the Pakistanis," the diplomat said.

Now, said ElBaradei: "We're looking into who else got ... materials, other than Libya or Iran." He said individuals in at least five countries were involved in trafficking that went back at least to the 1980s.

Dr Khan "was an important part of the process. Now he's cooperating with Pakistani authorities so hopefully we'll get as much information as we need," Mr ElBaradei said.

Mr ElBaradei said the clandestine process involved "items that were manufactured in other countries. There were items that were assembled in different countries. "There was diverting on ships," Mr ElBaradei added.

He said the IAEA "needs to follow through and know who was producing the centrifuges, who was producing different parts".

"What increases my anxiety is the ability of many countries now to produce equipment and materials that can lead to a nuclear weapons programme," Mr ElBaradei said.

He said export control was now "the most important issue" in preventing nuclear proliferation.

Nuclear technology exports are currently overseen by an informal international group called the Nuclear Suppliers Group.

Mr ElBaradei said the time had come "to have a system of export controls that insure that companies in different countries are controlled".

In Washington, CIA chief George Tenet said the agency worked with the British government to piece together the network of subsidiaries, scientists, front companies and finances operated by Dr Abdul Qadeer Khan.

"We detected the network, stretching across four continents, offering its wares to countries like North Korea and Iran," Mr Tenet said, adding Dr Khan was "shaving years off the nuclear weapons development timelines of several states, including Libya".

"Our spies penetrated the network through a series of daring operations over several years," he said.

The intelligence gathering confirmed Dr Khan's network was supplying countries with uranium enrichment centrifuges, and helped block deliveries of weapons to Libya.

Mr Tenet made the comments during a speech meant to defend the CIA, which has come under fire over the intelligence it produced on Iraq's alleged weapons of mass destruction programmes prior to the invasion.

"Through this unrelenting effort, we confirmed the network was delivering such things as illicit uranium centrifuges."-Agencies