The US and its western allies have stepped up a behind-the-scenes campaign to persuade Russia to back tough United Nations sanctions against Iran.
By Adrian Blomfield and Andrew Osborn in Moscow
They hope the West's case for robust action will be strengthened on Monday when the International Atomic Energy Agency (IAEA), the UN's nuclear watchdog, meets in Vienna to discuss a damning new report on Iran's atomic intentions.
According to the report, written by Yukiya Amano, the IAEA's tough-talking new chairman, Iran may be hiding "undisclosed activities related to the development of a nuclear payload for a missile".
The agency's findings are likely to pave the way for a Security Council resolution proposing a fourth round of sanctions on Iran.
Russia, along with China, ensured that the three previous rounds were considerably watered down. But in recent weeks, Moscow's patience with its long-standing ally appears to have evaporated and Russian officials have grudgingly talked of their support for some kind of sanctions.
Vladimir Chizhov, Russia's envoy to the European Union, conceded that dialogue with Iran was no longer working. "This prompts Moscow to think about options for sanctions."
Even so, diplomats privately say they expect Russia's cooperation to be, at best, limited.
In order to ratchet up the pressure on Iran's leadership, the United States, Britain, France and Israel are understood to back sanctions that would target Iran's central bank and financial sector, its main shipping and transportation companies and assets controlled by the country's powerful Revolutionary Guard.
But Russia favours a much more limited scope to sanctions, insisting that they should be narrowly targeted on individuals and companies directly involved in Iran's nuclear programme.
Diplomats concede that persuading Russia to change its position will be tough.
"Anything to do with proliferation we estimate the Russians will be cooperative," one said. "But when it comes to energy or arms, a whole different set of considerations comes into play."
Russia and China, both veto-wielding members of the Security Council, benefitted commercially from the previous rounds of sanctions. Russia sold Iran arms, China signed valuable energy deals and neither will surrender lucrative contracts easily.
Yet Western officials are still confident that they can win Russia over. Diplomats have made a number of discreet missions to Moscow to make power-point demonstrations, a source said.
Seeking to undermine those efforts, Iran on Sunday presented Russia with two rare Persian leopards — a gift personally solicited by Vladimir Putin, the Russian prime minister.
Persuading China, however, could well be a mission too far, according to one diplomatic source: "It's not very encouraging," he said. "We don't have much leverage."
Worryingly for the West, the number of sanctions naysayers seems to be growing.
This week, Hillary Clinton, the US secretary of state, will visit Brazil in an attempt to persuade its president, Luiz Inacio Lula da Silva, to end his increasingly cosy relationship with Iran.
Brazil is also pursuing commercial deals that the West says could allow Iranian banks that fund Tehran's nuclear programme to avoid sanctions.
