DUBAI: For Iranian envoys at an Asian affairs summit this week in Russia, it was the ultimate dream team: The Russian prime minister and China’s premier standing shoulder to shoulder and promising to keep Western influence at bay.

Iran’s leaders are now counting on the country’s two most powerful friends to remain by their side after the release Tuesday of a U.N. report suggesting that Tehran could be on the brink of having the capability to develop an atomic weapon.

Russia and China – both permanent members of the U.N. Security Council – are once again in the position of veto-carrying gatekeepers for any Western bids to tighten sanctions on Iran. They also hold important voices of dissent against warnings of military options by Israel and others, even as the White House insists that diplomacy is still the preferred path.

Tehran insists its nuclear program is peaceful, not for weapons production.

The choices for Moscow and Beijing could become even more complicated after the report by the U.N.’s International Atomic Energy Agency. Blocking possible attempts for tougher sanctions could help safeguard diplomatic and commercial interests – particularly China’s booming trade with Iran – but also may indirectly bolster the case for military action as a last resort, some experts said.

“It’s a difficult spot for them,” said Theodore Karasik, a security expert at the Dubai-based Institute for Near East and Gulf Military Analysis. “In the past, they complained about sanctions but eventually acquiesced or remained silent. It may play out like this again.”

It could, however, be a long process of negotiations and sound bite volleys before the next moves are clear.

Israel has stepped up warnings of a possible military strike in recent days. In the latest, Israel’s defense minister, Ehud Barak, said Tuesday that the option of a military strike is not “off the table” and rejected suggestions that Israel would be devastated by Iranian retaliation.

Russian President Dmitry Medvedev said a military strike on Iran could be a “catastrophe” for the Middle East.

“We should exhale, calm down and continue a constructive discussion of all issues on the Middle East agenda, including the Iranian nuclear program,” Medvedev said Tuesday in Berlin, a day after an Asian security summit in St. Petersburg that included Iran and pledges of closer cooperation between Chinese Premier Wen Jiabao and Russian Prime Minister Vladimir Putin.

China, too, remains strongly opposed to any use of force against Iran. But Foreign Ministry spokesman Hong Lei urged Tehran to show “flexibility and sincerity” as a way to encourage renewed international dialogue.

Beijing’s appeals also reflect that China has a lot to lose.

China became Iran’s biggest trading partner in 2009 with two-way commerce now hitting $36.5 billion and rising, according to the Iran-China Chamber of Commerce. China floods Iran with consumer goods, machinery and technological help for high-priority objectives such as missile upgrades and aerospace expertise for satellites.

In return, Iran helps China meet its soaring appetites for oil and petrochemicals. Iran, a member of the Organization of Petroleum Exporting Countries, currently supplies about 11 percent of China’s energy needs.

“China is economically connected with Iran while the U.S. is not,” said Yin Gang, an Iran expert at the Chinese Academy of Social Sciences. “That means China won’t fall into lockstep with the U.S. over Iran.”

But China also has competing concerns in the Mideast that could nudge Beijing toward backing at least limited new sanctions.

Iran’s chief regional rival, Saudi Arabia, is one of China’s top crude oil suppliers and Chinese companies are deeply involved in Saudi projects, including a $1.8 billion railway line between the holy cities of Mecca and Medina scheduled to be completed in 2013. China also is working hard to rebuild its reputation among Arabs after being slow to embrace the pro-reform uprisings in Libya and elsewhere.

“China won’t propose any action itself, but will listen to what the Arab states are saying,” said Yin. “China needs to keep a delicate balance on the issue. If it gets too close to Iran, it will not only displease the U.S., but also the Arab states.”

Last month, Russia and China vetoed a European-backed resolution in the Security Council denouncing Syria for the deadly crackdown on opposition protesters, saying it could open the door for military action similar to the NATO-led airstrikes in Libya.

For Russia, the vote also reinforced its overlapping political interests with Iran – a key backer of Syria’s Bashar Assad – even as trade ties have diminished sharply.

Many big Russian firms, including the No. 2 oil producer Lukoil, pulled out of Iran in recent years because of sanctions. And arms sales, the former backbone of trade, came to a near halt last year when Russian banned key weapons exports to Iran.

Russia built Iran’s first reactor, a $1 billion plant on the Gulf coast that began limited-power operations earlier this year.

Still, the head of the Moscow-based Middle East Institute, Yevgeny Satanovsky, said it appears unlikely that Russia will back stronger sanctions since they are widely perceived as ineffective.

“No matter what the Foreign Ministry says, Russian professionals are fully aware that Iran is moving closer to building a nuclear bomb and no sanctions are going to stop it,” he said.

In Tehran, President Mahmoud Ahmadinejad repeated Iran’s claim that it had no desire for nuclear weapons and only seeks reactors and labs for energy and research. He also called the IAEA chief, Yukiya Amano, a pawn of Washington who “delivers the papers that American officials hand on him.”

One senior U.S. official familiar with the IAEA report called it “pretty compelling” and predicted it would stiffen the resolve of U.S. allies, particularly in Europe, to step up pressure on Iran to prove that its nuclear program is peaceful as it claims. After the report was released, administration officials said more sanctions could be considered if Iran does not come up with suitable answers.

White House spokesman Jay Carney said Monday the U.S. continues to focus on using diplomatic channels to pressure Iran to abandon its nuclear program. But he added that the U.S. also will keep all options open. “We, of course, never remove from the table any option in a situation like this, but we are very focused on diplomacy,” he said.