U.N. inspectors have discovered new traces of highly-enriched uranium on nuclear equipment in Iran, deepening suspicions Tehran may still be concealing the full extent of its atomic enrichment program, diplomats said.

Several Western diplomats said there were signs Iran continued to pursue uranium enrichment research in secret and fear the goal is to acquire the capability to produce enriched-uranium fuel for weapons -- a charge Iran denies.

In its April report to the UN Security Council, the International Atomic Energy Agency (IAEA) said it took samples from equipment that had been acquired by a former research center at Lavizan-Shiyan. The center was razed in 2004 before IAEA inspectors could examine it.

The IAEA inspectors took swabs from vacuum pumps earlier this year which were subjected to microscopic particle analysis, diplomats said. Vacuum pumps are dual-use but are needed when enriching uranium with a cascade of interconnected centrifuges.

"Preliminary analysis by the IAEA showed traces of highly enriched uranium in the (pump) samples," a Western diplomat accredited to the IAEA told Reuters on condition of anonymity.

The former physics center at Lavizan, which advised the defense ministry, acquired some dual-use machinery useable for uranium enrichment, including vacuum pumps.

A diplomat in Vienna, where the IAEA is based, confirmed the new finding but warned against exaggerating its significance: "It's no smoking gun. There could be many explanations. But it increases pressure on Iran to come clean about Lavizan."...