By Michael Martina and Steve Gutterman
BEIJING/MOSCOW (Reuters) - Iran's proposal for a tour of its nuclear sites floundered on Thursday after China effectively rejected the invitation and Russia cautioned such a trip could never replace U.N. inspections or talks between Tehran and world powers.
The European Union has turned down Iran's offer to allow selected ambassadors accredited to the U.N. nuclear watchdog to visit two nuclear installations while snubbing those from the United States, Britain, France and Germany.
China, ahead of President Hu Jintao's state visit to the United States next week, said it would be "difficult" for its ambassador to the International Atomic Energy Agency (IAEA) in Vienna to go on the proposed Jan 15-16 tour.
"The Vienna representative is still in China right now, so it will be difficult for him to go to Iran," Foreign Ministry spokesman Hong Lei told a news briefing, without elaborating.
Just hours later, Russian Foreign Minister Sergei Lavrov told reporters in Moscow that such a visit could never replace regular inspections from the IAEA or talks with major powers on Iran's disputed nuclear program, echoing the EU position.
"Such a visit should in no way at all be seen as a substitution for IAEA inspections," Lavrov said, though he said the invitation deserved attention. He did not give a clear indication of whether Russia would agree to the tour.
Several U.N. Security Council resolutions have urged Iran to allow unrestricted inspections to defuse mistrust in Tehran's stance that it is enriching uranium only for electricity and other peaceful purposes, not for nuclear weapons.
Without the European Union, China and possibly even Russia, Tehran's trip proposal could collapse before Istanbul talks next week between Iran and the so called P5+1 group -- the five permanent members of the Security Council along with Germany.
Ali Asghar Soltanieh, Iran's envoy to the IAEA, said the nuclear tour would go ahead as planned and that he had seen no official response from either China or Russia.
Soltanieh said other ambassadors -- envoys from countries such as Egypt, Cuba, Venezuela and Syria -- would leave Vienna on Friday.
"Yes, we will definitely go tomorrow, they have all confirmed," he told Reuters.
The West is focused on stopping Iran taking what it suspects are steps to develop bomb-making capability under the cover of a declared civilian nuclear energy program. Russia and China have more complicated positions, and have watered down U.N. sanctions on Tehran adopted since 2006.
Moscow says the concerns about Iran's nuclear program are justified and has called on Tehran to allay the worries. But Russia has also warned Israel and the United States that pushing Tehran into a corner could spark conflict in the Middle East.
Some diplomats say the Iranian tour proposal appears to be a negotiating ploy designed to drive a wedge between the major powers, while buying time to keep stockpiling enriched uranium.
But analysts said that if that was the aim, it had failed.
"If that is what they were hoping to do, and probably they were, yes, it has failed," said David Hartwell, IHS Jane's Middle East and North Africa.
"There is widespread perception, certainly in the West, that this was a bit of a gimmick or public relations exercise."
Diplomats said that Russia and China were being discouraged by Western officials from joining the tour and that Moscow and Beijing would probably not want to be the only big powers to take part, especially ahead of Hu's trip to the United States.
"This (China's apparent rejection) is most likely related to President Hu Jintao's visit to the United States, showing that China respects the United States' position," said Shi Yinhong, international relations expert at Renmin University in Beijing.
"China would also feel there is no point in them going if the EU and Russia also don't."
Like Moscow, Beijing has backed U.N. Security Council resolutions leaning on Iran to suspend enrichment activity in exchange for trade and other incentives, but has opposed unilateral sanctions imposed by Europe and the United States.
"Given the pressure the EU and others have put on them to politely decline the invitation, I would be very surprised if either of them would have said yes," one European diplomat said on condition of anonymity.
(Additional reporting by Sabrina Mao and Ben Blanchard in Beijing, Steve Gutterman in Moscow and Fredrik Dahl in Vienna; writing by Guy Faulconbridge; editing by Philippa Fletcher)