"Look at the performance (data) of these centrifuges (in Brazil). They look very similar to the P2," sold by disgraced Pakistani scientist Abdul Qadeer Khan's network, Henry Sokolski, a former Pentagon official who now runs the Non-Proliferation Policy Education Center think tank in Washington, told AFP by telephone.

But International Atomic Energy Agency (IAEA) spokeswoman Melissa Fleming said "there is no indication so far that any other country shopped from the Khan network" beyond Iran, Libya and North Korea.

The Vienna-based IAEA is investigating Iran on US charges that Tehran is secretly developing nuclear weapons.

It is also trying to trace the operations of the Khan network, which has been exposed after Khan, the father of Pakistan's atomic bomb, was arrested earlier this year.

Centrifuges are used to enrich uranium, a process that makes what can be fuel for civilian reactors but also the explosive core of atomic bombs.

Brazil has since February blocked IAEA inspectors from coming to inspect its uranium enrichment facilities.

Sokolski said the Brazilians "do not want anyone to see the shapes of the casings and rotors" of their centrifuges.

IAEA inspectors are due to arrive in Brazil on October 15 to try to resolve the dispute.

The Brazilian science and technology ministry has stressed that IAEA inspectors "will only have access to parts indispensable to the application of guarantees, without revealing the cores of the centrifuges."

"After a five-month suspension, negotiations on the inspection of the plant have resumed," Science and Technology spokeswoman Vera Canfran told AFP.

Brazil, which has one of the world's largest uranium reserves, denied IAEA inspectors access in February and March to a uranium-enriching facility in Resende, in the state of Rio de Janeiro, saying it wanted to protect industry trade secrets.

IAEA director general Mohamed ElBaradei has said Brazil, which is widely believed to have a peaceful nuclear program, should not be an exception to IAEA norms.

IAEA spokeswoman Fleming said talk about Brazil as a possible Khan client "does not seem to fit what the IAEA knows about Brazil's nuclear program nor does it correspond to our talks with them so far."

Sokolski said "people say Brazil worked on its latest technology in the late 1990's," a reference to the period when the Khan network was especially active.

He said Brazil might have turned to the Khan network in order to make financial and technological shortcuts in developing centrifuges.

But experts close to the IAEA told AFP they did not think Brazil had tapped into the Khan network.

"They may have gotten some help from abroad with sensitive technology but Brazil has apparently developed centrifuges with some unique features," one expert, who asked not to be named, said, reinforcing the theory that Brazil is trying to hide its enrichment facilities in order to avoid industrial espionage.

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