Iran claims there is no suspicious activity at Parchin.

But Washington charges that Iran is secretly developing nuclear weapons at the explosives testing center, although this could be in non-nuclear "dry" tests of how such a weapon would function, that would leave no radioactive particles to find.

"The very first preliminary results have not found anything so far," a diplomat close to the Vienna-based UN watchdog International Atomic Energy Agency (IAEA) told AFP, stressing that these were still early indications that could change.

A second diplomat said the IAEA was waiting for more analysis from environmental swipes taken November 1 at Parchin, 30 kilometres (20 miles) southeast of Tehran.

Visits to sites like Parchin are beyond nuclear Non-Proliferation Treaty (NPT) safeguards requirements, which are limited to inspecting sites where there is sure to be nuclear material.

There may be no nuclear material present at Parchin if the Iranians did "dry testing" bomb simulations with non-radioactive metals.

In any case, a diplomat said, "we don't expect those samples to show any undeclared nuclear activities, after all the time Iran was given to sanitize those sites."

IAEA inspectors had first visited Parchin in January but saw only five out of what are a much larger number of buildings. The Iranian government had up until November refused a follow-up visit.

Final results are not expected to be finished until after a meeting November 24-25 in Vienna of the IAEA's 35-nation board of governors, which in September found Iran in non-compliance with the nuclear Non-Proliferation Treaty.

This opened the door to bring Iran before the UN Security Council, which could impose penalties such as trade sanctions to get Tehran to suspend all nuclear fuel work and cooperate fully with IAEA inspectors.

Diplomats say that Tehran appears to be showing more cooperation with IAEA investigators in order to avoid referral to the Security Council.

A diplomat close to the IAEA said the agency may decide that it wants to hold off on deciding on referral since new information is still coming in that will be needed before such a move can be taken.

In addition, there appears to be movement on the diplomatic front.

Iran wants to conduct sensitive nuclear work on its territory but is open to its uranium being enriched abroad, a day after Washington denied backing a proposal to resolve the nuclear row by letting enrichment be done in Russia, nuclear chief Ali Larijani said in Tehran Friday.

The swipes at Parchin are samples taken by rubbing a cotton cloth on surfaces to see if traces of radioactive particles can be found that would prove the presence of nuclear material.

Full analysis of the samples by spectrometry and other techniques can take up to six weeks.

David Donahue, a unit leader at the IAEA's Seibersdorf laboratory which analyzes the swipes said Friday that "some Parchin analysis has been done."

But he said that Seibersdorf had more swipes to analyze and would be doing more intensive tests on swipes already run through spectrometry experiments.

In addition, the IAEA is waiting for results from a second lab, in another country, to confirm the results.

Donahue said IAEA inspectors take six swipes at a time so that they have replicas and then have at least two analyzed and store the others in archives.

Donahue refused to indicate the total number of swipes taken at Parchin November 1 but he said: "It's not hundreds."

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