The announcement by Foreign Minister Kamal Kharazi comes on the eve of a new visit by inspectors beginning Sunday that will last until October 31, the UN deadline for Tehran to prove it is not trying to develop nuclear weapons.
"Iran does not have a nuclear weapons programme nor does it intend to embark on one," Kharazi said in his address before the UN General Assembly.
"Thus we have nothing to hide and, in principle, have no problem with the additional protocol," as the document that would allow the unscheduled inspections is called.
In Vienna, headquarters of the UN's International Atomic Energy Agency (IAEA), diplomats said earlier Thursday that more traces of highly enriched uranium had been found in Iran.
The United States says the Islamic regime -- part of US President George W. Bush's "axis of evil" -- is producing the uranium in a bid to manufacture nuclear weapons. Iran has rejected the claim.
The latest uranium traces were found at a site that, according to one diplomat in Vienna, had been blocked to UN inspectors for months and had undergone "considerable modifications" when they were finally allowed access.
The United States says that Iran does not need highly enriched uranium for a reactor it is building in the southern city of Busheher with help from Russia. It says the enriched fuel is not needed for civilian nuclear energy programmes.
Bush said Thursday that Iran's alleged nuclear weapons programme would be on the agenda when he hosts a summit with Russian President Vladimir Putin beginning on Friday.
He added that he had also raised Iran with other world leaders while in New York for the UN General Assembly on Tuesday and Wednesday.
"The response was very positive and people understand the danger of Iranians' having a nuclear weapon program," Bush said.
"It is very important for the world to come together to make very clear to Iran that there will be universal condemnation if they continue with their nuclear weapons programme."
Kharazi again shrugged off the threat.
"Iran will vigorously pursue its peaceful nuclear programme and will not give in to unreasonable demands that are discriminatory, selective and go beyond the requirements of non-proliferation in accordance with existing IAEA instruments," he said.
He said Tehran wanted assurances that signing the additional protocol to the Non Proliferation Treaty (NPT) would be "solely utilised to enhance confidence" in Iran's claims.
As it regularly does when discussing questions about its nuclear programme, Kharazi accused Israel -- which has never acknowledged its own nuclear warheads -- was testing advanced tactical nuclear weapons.