A new report by the UN atomic watchdog validates Iran's progress in its "peaceful" nuclear activities despite international sanctions, the country's envoy to the agency said on Thursday.
The International Atomic Energy Agency's report said Iran had accelerated the installation of advanced uranium enrichment equipment at its central Natanz plant, and was potentially opening up a second route to developing the bomb.
Ali Asghar Soltanieh, speaking to Fars news agency in Vienna, where the IAEA is based, said the report was proof of Iran's "technical and scientific success".
It also showed there was "no evidence of diversion in nuclear material and activities toward military purposes" and that "all the centrifuges and each gram of uranium are under the supervision of the agency," he said.
In its report issued on Wednesday, the IAEA outlined further progress at a reactor under construction at Arak, in central Iran, which Western countries fear could provide the Islamic republic with plutonium if the fuel is reprocessed.
Highly enriched uranium and plutonium can both be used in a nuclear weapon.
Soltanieh did not comment on the developments at the Arak reactor.
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The IAEA report showed Iran has so far produced 324 kilograms (714 pounds) of 20-percent enriched uranium, 44 kilograms more than three months ago, but that 140.8 kilograms had been diverted to fuel production, up from 111 kilograms.
Experts say about 240-250 kilograms are needed for one bomb.
The UN Security Council has passed numerous resolutions calling on Iran to suspend all enrichment and heavy water activities of the kind under development at Arak.
It has imposed four rounds of sanctions.
Last year additional unilateral US and EU sanctions targeting Iran's oil exports and its financial system began to cause real problems for the Islamic republic's economy.
Israel, the Middle East's sole if undeclared nuclear-armed state, has refused to rule out military action against Iran, as has US President Barack Obama. Iran insists its atomic activities are peaceful.
Parallel diplomatic efforts to resolve the impasse, most recently in six-power talks with Iran in Kazakhstan in April, have failed to make concrete progress.