An Iranian news agency FARS has reported that a top U.N. nuclear official visited Iran's normally restricted atomic sites last week. The agency quotes Iran's envoy to the International Atomic Energy Agency, Ali Asghar Soltanieh, as saying the head of the IAEA's safeguards division, Herman Nackaerts, spent five days in Iran last week. Soltanieh said Nackaerts and his delegation visited the Bushehr nuclear plant, enrichment facilities in Fordo and Natanz, nuclear sites in Isfahan and the Arak heavy water research facility. Soltanieh said the group was allowed to visit research sites for advanced centrifuges, and that there were talks on how to expand cooperation with the IAEA. Iran has said it is prepared to take steps to resolve its nuclear dispute with Western powers in return for reciprocal steps from the international community. The IAEA has said Iran did not cooperate with its recent probe of Western allegations that Iran is trying to produce nuclear weapons. Iran says its nuclear program is for peaceful purposes. Western nations have imposed a series of economic and political sanctions on Iran to pressure it to stop enriching uranium.