The Islamic republic's representative to the International Atomic Energy Agency (IAEA) told state television that traces of enriched uranium found by the UN body in August at the Kalaye Electric Company near Tehran came into the country on imported equipment.
He explained that given the level of enrichment was over 50 percent, the traces could have only come from overseas because "such enrichment requires a number of centrifuges to be working over a long period of time" -- in other words something that he asserted has not taken place in Iran.
Salahi added the company near Tehran had been producing machinery for a nuclear facility located in Natanz, 250 kilometres (150 miles) south of Tehran, where inspectors had earlier found traces of enriched uranium.
Officials here say enrichment experiments have only just got underway.
Meanwhile, government spokesman Abdollah Ramezanzadeh told reporters that Iran would not accept any restrictions on its bid to generate nuclear power, rejecting international demands for tougher safeguards on Teheran amid suspicions the programme is merely a cover for nuclear weapons development.
"The Islamic Republic of Iran rejects any restrictions on the peaceful use of nuclear technology," Ramazanzadeh told reporters.
"Up to now, we have cooperated with the IAEA beyond our commitments" under the nuclear Non-Proliferation Treaty (NPT), he said, adding that future cooperation with the IAEA depended on "how our negotiations progress".
The IAEA has given Iran until October 31 to answer all its questions concerning allegations that it is seeking to develop atomic weapons, and has also called on the country to cease uranium enrichment.
The agency has also called on Iran to sign an additional protocol to the NPT, which would allow inspectors to conduct surprise visits to suspect sites. IAEA teams are only currently permitted to make pre-arranged visits, although Iran says it is cooperating beyond the terms of the NPT.
"The issue of the additional protocol is not an issue to be dealt with in one or two sessions," Ramazanzadeh said, shrugging off IAEA calls for Iran to sign the text unconditionally and immediately.
It is also discussing the additional protocol with the IAEA, in order to clear up what it describes as "ambiguities" in the text.
The United States has charged that the Iranians have used Kalaye to test centrifuges used to make highly enriched uranium that can be used to make atomic bombs.
Ramazanzadeh repeated official denials of the allegations.
"We are ready to have full cooperation with the IAEA, and according to our religious teachings and special circumstances... we are in no way intending to use nuclear energy for anything other than peaceful purposes," he said.
European foreign ministers meeting in Brussels Monday were expected to renew their demands for Tehran to sign the additional protocol to the NPT. The European Union has warned that, without credible guarantees, it will review its economic ties with Iran.
But Ramazanzadeh also shrugged off the EU pressure.
"We are not a people who will change our policies under pressure or threats, he said, but added that "we have good relations with the Europeans and we hope that continues."