Pakistan last week admitted that Abdul Qadeer Khan, the disgraced scientist who fathered the country's nuclear weapons program, had sold Iran centrifuges, which are used to enrich uranium into what can be either fuel for nuclear power plants or the explosive core of atom bombs.

"The centrifuge parts will be sent to the International Atomic Agency Agency laboratory (IAEA) in Seibersdorf" near Vienna, which will analyze and compare them with centrifuge components Khan sold to Iran, a Western diplomat close to the IAEA told AFP.

The IAEA is investigating contamination by microscopic particles of highly enriched uranium (HEU) found in Iran at a workshop in Tehran, at a pilot enrichment plant at Natanz and at other sites where there were centrifuges.

Iran, which says its nuclear program is for the peaceful purpose of making electricity, claims the HEU-contaminated equipment came from imported machinery and not from enrichment activities in Iran.

IAEA chief Mohamed ElBaradei has stressed that Pakistan and other countries involved in an international nuclear black market that supplied Iran must cooperate if the IAEA is to answer US charges that Tehran is secretly developing atomic weapons.

Non-proliferation analyst David Albright told AFP that Iran's sending the centrifuge parts was a compromise hammered out in months of talks as the Pakistani government refuses to let IAEA experts inspect centrifuge sites in Pakistan.

"It's a compromise but I'm not sure it will work," in resolving the issue, said Albright, a former UN nuclear inspector and head of the Washington-based Institute for Science and International Security (ISIS).

"The worry is that parts have been tampered with deliberately or accidentally," Albright said.

Also, Albright said the IAEA was "relying on the word of the Pakistanis" to know "if the parts come from where they need to come from."

A Western diplomat said the parts being shipped from Pakistan should come from the same set of centrifuges that were used at the Tehran workshop, where the highest HEU level was found, "otherwise it wouldn't serve any purpose."

Another diplomat close to the IAEA said the agency would be "happy when the parts actually arrive" as the investigation was a very delicate matter.

When they get the centrifuges from Pakistan, IAEA technicians will be checking for HEU contamination and to see whether the "signature" or isotope configuration of the contamination at the sites in Iran matches that of the parts from Pakistan.

ElBaradei has reported that Iran hid sensitive nuclear activity for almost two decades but says "the jury is still out" on whether Tehran has a covert atomic weapons program.

He said in a report in November that data "to date tends, on balance, to support" Iran's claim that the HEU traces found by IAEA inspectors came from contaminated equipment.

But ElBaradei said his agency is continuing to investigate whether the contamination might be due to undeclared enrichment activities by Iran, or from imported uranium.

Khan was arrested in Pakistan last year but the government is not allowing the IAEA or any foreigners access to him.

IAEA deputy director general Pierre Goldschmidt said in a report to the agency on March 1 that inspectors had taken environmental samples at a site where the centrifuge parts had been stored in a third country prior to their shipment to Iran.

Diplomats said the third country was the United Arab Emirates.

The United States wants Iran brought before the UN Security Council for possible sanctions but is still backing an effort by Britain, France and Germany to resolve the issue diplomatically.

Albright said the United States was putting "tremendous pressure" on Pakistan, which has nuclear weapons but is not a signatory to the nuclear Non-Proliferation Treaty (NPT) under which the IAEA operates, to cooperate with the IAEA investigation.

"I think Pakistan is going to have to relent at some point and allow the IAEA to talk to Khan," Albright said.

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