(Restyles, adds U.S. comment)

By Oleg Shchedrov and Parisa Hafezi

TEHRAN, Oct 16 (Reuters) - President Vladimir Putin made clear to Washington on Tuesday that Russia would not accept military action against Iran and he invited Iranian President Mahmoud Ahmadinejad to Moscow for talks.

Putin made the invitation to Ahmadinejad, shunned by the West which fears his nuclear programme is a cover for building atomic weapons, after meeting him and leaders of other Caspian Sea states who ruled out any strikes on Iran from their region.

Dates for Ahmadinejad's visit would be arranged through diplomatic channels, RIA news agency quoted a statement by the two leaders as saying.

Earlier, in comments aimed at the United States, Putin said during his talks in Iran: "We should not even think of using force in this region."

"We need to agree that using the territory of one Caspian Sea (state) in the event of aggression against another is impossible," he told the presidents of Iran, Azerbaijan, Kazakhstan and Turkmenistan at a summit of Caspian Sea states.

Western nations accuse Tehran of seeking atomic weapons, a charge Tehran denies. Washington has refused to rule out the use of force if diplomacy fails to resolve the row.

Asked about Russia's invitation to Ahmadinejad, a U.S. State Department official said: "It's up to the Russians to determine how they want to manage their bilateral relations with Iran."

Putin's remarks about territory also appeared aimed at ex-Soviet Azerbaijan, where the U.S. military has inspected airfields. Russian media have suggested Washington might be trying to negotiate the right to use its military facilities. Baku denies this.

Russia is annoyed at what it sees as the West's attempts to end its influence in former Soviet states.

In a final declaration, the Caspian nations backed Putin's call, saying "under no circumstances will they allow (the use of their) territories by third countries to launch aggression or other military action against any of the member states".

The countries also backed the rights of signatories to the Non-Proliferation Treaty -- which includes Iran -- to develop peaceful nuclear energy.

Ahmadinejad, who says Tehran will not stop atomic work that he insists is peaceful, praised the Caspian declaration.

Putin's trip to Iran, the first made by a Kremlin leader since 1943, has been watched because of Russia's potential leverage, on behalf of fellow world powers, to rein in Iran using its trade and nuclear supply ties with Tehran.

PROGRESS ON BUSHEHR PLANT

Russia is building Iran's first atomic power plant in the port city of Bushehr. Russia says Iran is behind in payments for the plant, causing construction delays, but Iran says it is up to date and that Moscow is bowing to Western pressure.

Putin told Iranian media he could not provide guarantees for when fuel for the plant, also delayed, would be delivered. He said this would depend on discussions about the contract. The two sides agreed, Russian news agencies said, that Russia would complete work according to the "agreed timetable".

The timetable has regularly slipped and Putin's comments are likely to disappoint Iranian officials, who before his arrival, said they expected "good news" about Bushehr.

Putin turned up in Iran after shrugging off a Russian report about a plot to kill him during the trip. Russian officials had suggested he might change his plans. Iran dismissed the report.

Putin had bilateral talks with Ahmadinejad and also met Supreme Leader Ayatollah Ali Khamenei, who holds ultimate authority in Iran.

The U.N. Security Council has imposed two rounds of limited sanctions on Iran, which were backed by Russia and five other world powers -- the United States, France, Germany, Britain and China. Washington and Paris are pushing for tougher steps.

Moscow says it sees no evidence of a military programme and is resisting Western calls for new sanctions. Russia has also been alarmed by talk in the West that the row could result in conflict. France has warned of a possible war.

But, in Washington, State Department spokesman Tom Casey was confident of Moscow's support as the U.S. and others push for more punitive action.

"We fully expect that we will have support from the Russian Government for our longstanding policy that has been crafted, not by the U.S. but by the members of the Security Council, starting with the P-5+1," he said, referring to the permanent five members of the U.N. Security Council plus Germany.

(With additional reporting by Fredrik Dahl, Reza Derakhshi and Zahra Hosseinian, and Sue Pleming in Washington)

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