Tim Wall and Anna Arutunyan

Prime Minister Vladimir Putin used the occasion of his annual meeting with the Valdai Club to issue a strong defence of Iran against the threat of force or new sanctions imposed by the West.

According to comments confirmed by his press secretary, Dmitry Peskov, Putin told foreign experts at the Valdai Club meeting that "any use of force, delivering any kind of strike, won't help, won't solve the problem. On the contrary, it will hurt the entire region. As for sanctions, they won't bring the desired effect."

His comments come as Russia, Iran and Israel are embroiled in a dispute over the possible supply of S-300 missiles to Iran under a deal with Moscow, and an alleged secret visit to Russia last week by Israel's prime minister, Benyamin Netanyahu.

Russian officials are thought to have promised the United States and Israel that Moscow will not deliver the defensive missiles to Iran. Israel has threatened to attack Iranian nuclear facilities before nuclear weapons can be produced from what Iran claims are purely civilian nuclear operations.

The dispute over the missiles could blow up into a major row between the US and Russia, and potentially derail plans furthered by President Barack Obama during his visit to Moscow in July for a reset in relations.

Under a potential "grand bargain", the US could cancel its planned missile defence shield in Europe, in return for Russia suspending sales of missiles to the Iranian regime and persuading it to abandon plans to build nuclear weapons.

Russian officials initially denied that The Arctic Sea, a ship reported hijacked in the Baltic in July, had been carrying Russian S-300 missiles, or that Netanyahu had visited Moscow for talks with Russian leaders.

The Arctic Sea, set to deliver a shipment of timber to Algeria, disappeared along with 15 Russian crew members on board. The journalist who reported the disappearance, Mikhail Voitenko, has fled to Thailand after complaining of phone threats.

Netanyahu himself briefly disappeared off the radar screen last week amid leaks that he had made a secret trip to Moscow to discuss arms shipments to Iran and Syria - and possibly even the mysterious cargo aboard the Arctic Sea.

Yedioth Ahronoth reported Wednesday that Netanyahu had actually spent Monday discussing arms deals in Moscow. He had even reportedly rented a private jet to escape media attention. Russia's Kommersant daily, meanwhile, cited a high-placed Kremlin source as confirming Netanyahu's visit.

British newspaper The Sunday Times has cited security sources in Israel and Russia as saying that Mossad, the Israeli secret service, had tipped off Russian authorities about a group of former Russian officers and criminals loading the S-300s on to The Arctic Sea in Kaliningrad, and that Russian authorities had later sent a nuclear submarine and other vessels to recover the missiles.

But in the last few days, both Putin and Sergei Lavrov, the foreign minister, have given more non-committal answers - neither confirming nor denying either report.

Ariel Cohen, a Russia expert with US think tank the Heritage Foundation who was at the Valdai meeting with Putin, said the prime minister deflected a question about Netanyahu's visit.

"Somebody said, what can you tell us about the visit?" Cohen said by telephone on Monday. "And [Putin] said, ‘What can you tell us about the visit? Do you have any facts? If you have facts, then I would like to hear facts. And if you don't have facts, then I'm not commenting.'"

Putin also said, according to Cohen: "Iranian rhetoric against Israel that includes the destruction or annihilation of Israel is totally unacceptable. It's up to Iran to clarify its position to Israel and the rest of the world."

Putin's comments at the Valdai meeting signal that Russian support for further sanctions against Tehran are "not forthcoming. Clearly, this can be a serious blow to the reset in relations. This undermines the future outlook for Russia-US relations," Cohen said.

Another participant in the meeting, Angela Stent of Georgetown University, said that while Washington and Moscow had achieved progress on cooperation over Afghanistan, the Iranian nuclear issue remained "a significant problem" in Russia-US relations.

"The US also is concerned about possible Israeli action if certain weapons - such as the S-300 - are delivered to Iran," Stent said in e-mailed comments. "If the US were to announce that it has decided not to deploy missile defense components in Central Europe, and Russia does not cooperate in imposing tougher sanctions on Iran, this could seriously impact the reset process."

Russian analysts said, however, that abandoning its commitments to Iran, a traditional ally, was not something Moscow could do easily.

"When Obama first came to Moscow he wanted to improve relations by striking a deal," said Anatoly Utkin, director of the Center for International Research at the Russian Academy of Sciences. "They stop digging trenches for the missile shield in Eastern Europe, and in return we put pressure on Iran. But this is not a worthwhile policy towards Iran for Russia."

Iran had stayed out of all military conflicts in the CIS, something that Russia appreciated, Utkin said.

"Also, Iran ships a third of its oil to China. Russia has good relations with China," he added. "To pressure Iran will mean they will not get this oil. ... Why would Russia want to put pressure on Iran? It's close to us. We sell it weapons."