Diplomats from six nations and the Arab League toured Iran's main uranium enrichment facility on Sunday in a visit organized by Tehran in hopes of bolstering its assurances that its nuclear work is entirely peaceful.

The United States and some of its allies have for years accused Iran of seeking to develop a nuclear weapons capability under the cover of a civil nuclear power program, and Washington — which was not invited — mocked Iran's event as a "magical mystery tour." It said it was no substitute for fully cooperating with the U.N. nuclear watchdog to prove that its nuclear work has no military dimension.

The visit to the enrichment facility near the city of Natanz and another a day earlier to a plutonium-producing heavy water reactor under construction near Arak was an attempt by Iran to build support before more talks with the U.S. and other world powers on its disputed atomic program in Istanbul, Turkey, this month.

However, the only two participants in those talks to be invited for the weekend tour — China and Russia — turned Tehran down. Iran was likely hoping to win over Moscow and Beijing, which in the past have differed with the other countries involved in the talks over the issue of sanctions.

The European Union also rejected the invitation, saying the job should be left up to U.N. nuclear inspectors.

In a sign of a highly choreographed event, state TV and other Iranian media reported remarks by senior Iranian officials hosting the delegation but not from any of the visiting ambassadors, who represent six nations and the Arab League at the U.N.'s Vienna-based International Atomic Energy Agency. The six nations are Egypt, Cuba, Syria, Algeria, Venezuela and Oman.

Journalists for foreign media outlets were also not allowed to accompany the delegation.

Speaking on the visitors' behalf, Iran's ambassador to the U.N. agency, Ali Asghar Soltanieh, said, "They realized that claims by the West of clandestine and underground activities were baseless."

He was also quoted by the Fars news agency as saying the visitors could see for themselves that the enrichment plant had monitoring cameras in place from the IAEA.

The agency has had inspectors in Iran but complains from time to time about restrictions on their work and says it has not been able to verify whether Iran's program is solely peaceful.

Iran's nuclear chief and acting foreign minister, Ali Akbar Salehi, was quoted by state TV as saying, "Our justified stance was clarified through the visit."

The enrichment plant and the heavy water reactor — both in central Iran — could be used to make the fissile core of nuclear warheads. Iran denies such an intention and says it only has peaceful aims like generating power and making isotopes for treating cancer patients.