The Tehran government confirmed on Tuesday that it has invited world powers and its allies in the Arab and developing world — but apparently not chief critic the United States — to tour Iranian nuclear sites before a high-profile meeting late January on its disputed nuclear programme.

The Associated Press reported the invitation to tour the facilities on Monday, citing a letter from a senior Iranian envoy that suggested the visit take place the weekend of January 15 and 16.

A diplomat familiar with the invitation said the U.S. and the other Western powers in the group were not invited, in an apparent attempt to split the six powers ahead of planned talks on Iran's nuclear programme this month.

An Iranian official speaking from a European capital said facilities to be visited include the nuclear enrichment facility at Natanz and the Arak site where Tehran is building a plutonium-producing heavy water reactor. Both facilities are considered suspect by the West because they could be used to make the fissile core of nuclear warheads.

On Tuesday, Foreign Ministry spokesman Ramin Mehmanparast confirmed the offer, saying it went to “the E.U, the non-aligned movement and representatives from 5+1 countries.”

The “5+1” countries are the six world powers negotiating with Iran over its nuclear programme — the five permanent U.N. Security Council members (the United States, Britain, France, Russia and China {hbox) plus Germany.

Mr. Mehmanparast said Iran would identify the invited countries at a later time.

But a diplomat familiar with its contents said it was mailed to Russia, China, Egypt, the group of nonaligned nations at the U.N. International Atomic Energy Agency, Cuba, Arab League members at the IAEA, and Hungary, which currently holds the rotating EU presidency.

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