While Russia and China are ready to back protest-rocked Iran under threat by US President Donald Trump, that support would diminish in the face of US military action, experts told AFP.
Iran is a significant ally to the two nuclear powers, providing drones to Russia and oil to China. But analysts told AFP the two superpowers would only offer diplomatic and economic aid to Tehran, to avoid a showdown with Washington.
"China and Russia don't want to go head-to-head with the US over Iran," said Ellie Geranmayeh, a senior policy expert for the European Council on Foreign Relations think tank.
Tehran, despite its best efforts over decades, has failed to establish a formal alliance with Moscow and Beijing, she noted.
If the United States carried out strikes on Iran, "both the Chinese and the Russians will prioritize their bilateral relationship with Washington", Geranmayeh said.
China has to maintain a "delicate" rapprochement with the Trump administration, she argued, while Russia wants to keep the United States involved in talks on ending the war in Ukraine.
"They both have much higher priorities than Iran."
- Ukraine before Iran -
Despite their close ties, "Russia-Iranian treaties don't include military support" -- only political, diplomatic and economic aid, Russian analyst Sergei Markov told AFP.
Alexander Gabuev, director of Carnegie Russia Eurasia Center, said Moscow would do whatever it could "to keep the regime afloat".
But "Russia's options are very limited," he added.
Faced with its own economic crisis, "Russia cannot become a giant market for Iranian products" nor can it provide "a lavish loan", Gabuev said.
Nikita Smagin, a specialist in Russia-Iran relations, said that in the event of US strikes, Russia could do "almost nothing".
"They don't want to risk military confrontation with other great powers like the US -- but at the same time, they're ready to send weaponry to Iran," he said.
"Using Iran as a bargaining asset is a normal thing for Russia," Smagin said of the longer-term strategy, at a time when Moscow is also negotiating with Washington on Ukraine.
Markov agreed. "The Ukrainian crisis is much more important for Russia than the Iranian crisis," he argued.
- Chinese restraint -
China is also ready to help Tehran "economically, technologically, militarily and politically" as it confronts non-military US actions such as trade pressure and cyberattacks, Hua Po, a Beijing-based independent political observer, told AFP.
If the United States launched strikes, China "would strengthen its economic ties with Iran and help it militarize in order to contribute to bogging the United States down in a war in the Middle East," he added.
Until now, China has been cautious and expressed itself "with restraint", weighing the stakes of oil and regional stability, said Iran-China relations researcher Theo Nencini of Sciences Po Grenoble.
"China is benefiting from a weakened Iran, which allows it to secure low-cost oil... and to acquire a sizeable geopolitical partner," he said.
However, he added: "I find it hard to see them engaging in a showdown with the Americans over Iran."
Beijing would likely issue condemnations, but not retaliate, he said.
Hua said the Iran crisis was unlikely to have an impact on China-US relations overall.
"The Iranian question isn't at the heart of relations between the two countries," he argued.
"Neither will sever ties with the other over Iran."
