The IAEA and Iran are "going around in circles" after 10 failed meetings on Tehran's suspected nuclear weapons research, the head of the UN nuclear watchdog said Monday.
"To be frank, for some time now we have been going around in circles," Yukiya Amano told a closed-door quarterly meeting of the International Atomic Energy Agency's board of governors.
"This is not the right way to address issues of such great importance to the international community, including Iran," he said, according to the text of his speech in Vienna.
"We need to achieve concrete results without further delay to restore international confidence in the peaceful nature of Iran's nuclear activities."
In these 10 rounds, the latest on May 15, the IAEA has pressed Iran to grant access to documents, people and sites involved in Tehran's alleged efforts to develop atomic weapons.
Iran says the IAEA's findings are based on faulty intelligence from foreign spy agencies such as the CIA and Israel's Mossad -- intelligence it complains it has not even been allowed to see.
The sites that the agency wants to visit include the Parchin military base near Tehran, where it suspects Iran built a large explosives containment vessel to conduct experiments that the IAEA says would be "strong indicators of possible nuclear weapon development".
The IAEA's chief inspector Herman Nackaerts told a closed-door meeting last week that extensive construction activity spotted by satellite at Parchin meant that the agency may now be unable to find any evidence if its inspectors are ever allowed in.
Parallel negotiations between Iran and six world powers -- the US, China, Russia, Britain, France and Germany -- are also stalled following the latest gathering in Almaty, Kazakhstan in early April.
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This diplomatic track, on hold until after Iran's June 14 elections, is focused more on Iran's current activities which, as the IAEA's latest quarterly report circulated on May 22 made clear, Iran has continued to expand in spite of UN Security Council resolutions calling for a suspension.
In particular, and despite of sanctions aimed at preventing such advances, it has boosted its capacity to enrich uranium, which in its highly purified form can be used in a nuclear weapon. Iran says it needs the material for power generation and medical isotopes.
According to the IAEA report, Iran has also converted a portion of its medium-enriched uranium into another form in order to make reactor fuel, which is difficult -- but not impossible -- to convert back.
But analysts say the rate of conversion is too low to prevent Iran's uranium stockpile from growing, that its output could triple once new machinery is up and running and that Tehran is producing more than it currently needs.
This conversion of 20-percent enriched uranium "is a ray of light but there are still some pretty dark clouds around," Shannon Kile, nuclear expert at the Stockholm International Peace Research Institute (SIPRI), told AFP.
One such source of additional worry is Iran's progress, also outlined in the latest IAEA report, in building a new reactor at Arak which could in theory provide Iran with plutonium, if the fuel is further processed.
Plutonium is an alternative to highly enriched uranium for a nuclear weapon.
Arak "shows that this issue is not just about 20-percent enriched uranium stockpiles. This is a broader picture," said one senior Western diplomat in Vienna.
The IAEA's 35-nation board of governors was expected however to refrain from any action over Iran at its board meeting that started on Monday, in part because of Iran's presidential elections on June 14.
"If I interpret the tea leaves correctly from the P5+1, the powers will essentially be prepared to kick the can down the road, at least for another few months," Mark Hibbs, analyst at the Carnegie Endowment for International Peace, told AFP.