Vienna, Austria ? U.N. inspectors have found traces of highly enriched uranium on equipment from an Iranian research center linked to the military, diplomats said Friday – a revelation likely to strengthen U.S. arguments that Tehran wants to develop nuclear arms.

The diplomats, who demanded anonymity in exchange for divulging the confidential information, cautioned that confirmation still had to come through other laboratory tests.

Initially, they said the density of enrichment appeared to be close to or above the level used to make nuclear warheads. But later a diplomat accredited to the International Atomic Energy Agency said it was below that, although higher than the low-enriched material used to generate power and heading toward weapons-grade level.

Still, they said, further analysis could show that the find matches others established to have come from abroad. The IAEA determined earlier traces of highly enriched uranium were imported on equipment from Pakistan that Iran bought on the black market during nearly two decades of clandestine activity.

Even then, nevertheless, the find would be significant.

Because Iran has previously denied conducting enrichment-related activities at the site, the mere fact the traces came from there bolsters arguments that it has hidden parts of a program that can create the fissile material used in nuclear warheads. Additionally, the site’s connection to the military weakens Iranian arguments that its nuclear program is purely civilian.