UN inspectors have found traces of highly enriched uranium at an Iranian research center linked to the military, diplomats said Friday, which could strengthen US 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. But they said the density of enrichment appeared to be close to or above the level used to make nuclear warheads. Still, they said, further analysis could show that the find matches others established to have come from abroad. The International Atomic Energy Agency determined earlier traces of weapons-grade uranium were imported on equipment from Pakistan that Iran bought on the black market during nearly two decades of clandestine activity discovered just over three years ago.