Iran is trying to launch the tour as a gesture of transparency ahead of the Jan. 20-22 talks in Istanbul, Turkey. However, major powers Russia, China and the European Union refused the Iranian invitation. The EU said it should be up to inspectors from the U.N.'s International Atomic Energy Agency to verify whether Iran's program is entirely peaceful.

Iran's offer did not include the US, one of its biggest critics internationally, nor three other Western nations that have been critical of the Iranian program — Britain, France and Germany — and many saw the tour as an attempt to divide the nations conducting the nuclear talks.

Ambassadors to the U.N. atomic energy agency from Egypt, Cuba, Syria, Algeria, Venezuela, Oman and the Arab League arrived in Tehran early Saturday and visited the unfinished heavy water reactor near Arak in central Iran, state TV reported.

The group is expected to tour Iran's main uranium enrichment facility near Natanz on Sunday.

AP