The International Atomic Energy Agency said Libya and "other member states" of the IAEA would have to cooperate in investigating the Pakistani-run black market that supplied these designs, in a confidential report obtained by AFP ahead of a meeting of the agency's board of governors September 13.

"We've had excellent cooperation" since Libya agreed in December to dismantle its covert programs to develop weapons of mass destruction, said IAEA spokesman Mark Gwozdecky.

The United States has called on Iran, which the IAEA is also probing charges of secretly developing atomic weapons to be as forthcoming about its nuclear program as Libya has been.

But Gwozdecky said "critical questions" remained about whether Libya had made copies of the nuclear weapons designs it had obtained through the black market run by disgraced Pakistani scientist Abdul Qadeer Khan.

The report said the IAEA was doing "forensic analysis to establish inter alia the dates of the printing and the source of the paper" of the designs.

"We want to know if copies were made," Gwozdekcy said, adding that the probe would focus on "getting information from the source of these (arms design) drawings."

The report said the IAEA "would benefit greatly" from information "from the provider of the weapon design."

The weapons designs are believed to be Chinese blueprints, given to Pakistan in the 1980's, non-proliferation expert Joseph Cirincione said.

He said the IAEA was "clearly saying that China should step up and say if it provided this design."

"Reading between the lines you can see the IAEA inspectors are frustrated they are not getting more cooperation from other states involved in this transaction," Cirincione of the Washington-based Carnegie Endowment for International Peace told AFP.

"The good news is that Libya is providing lots of information and cooperation.

"The bad news is that Libya seems to be holding back some information, particularly related to their suppliers and the possible receivers of some of the designs and equipment," Cirincione said.

IAEA inspectors had earlier this year found contamination from highly enriched uranium (HEU), which could be weapons-grade, as well as low enriched uranium on gas centrifuge equipment in Libya.

This was similar to HEU contamination that has been found in Iran on centrifuge parts.

Monday's report said the IAEA had received so-called environmental swipes taken as samples by an unidentified state, apparently Pakistan, "from the suspected supplier of the components."

It said the state had "shared the sample data with the agency" but that the agency needed to take its own swipe samples to complete the investigation.

This could help the IAEA figure out whether the contamination it has found in Iran came from abroad or was the result of secret Iranian attempts to enrich uranium, Cirincione said.

The IAEA report said that "nearly all of the equipment involved in Libya's past nuclear activities was obtained from abroad, often with the involvement of private intermediaries."

It said investigating these foreign connections was "by nature somewhat slow ... and will continue for some time."

But the report said "good cooperation" from Libya "has enabled the agency to build an understanding of Libya's previously undeclared nuclear program."

The agency said the cooperation was so good that it would not need to compile a further report on Libya for the next board meeting in November and would monitor Libya through normal safeguard procedures.

The IAEA, the UN organization that verifies adherence to non-proliferation safeguards, has been overseeing Libya's disarmament, which Tripoli agreed to last December 19 with the United States and Britain.

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