Addressing representatives of the 35 nations on the IAEA board, Yukiya Amano said 10 rounds of fruitless negotiations had been held with Tehran since January 2012, the British newspaper The Daily Telegraph reported.
"To be frank, for some time now we have been going around in circles," he said.
"We need to achieve concrete results without further delay to restore international confidence in the peaceful nature of Iran's nuclear activities," Amano added.
Iran has installed 13,555 centrifuges to enrich uranium inside its largest nuclear plant, the latest IAEA report on Iran's nuclear program found.
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