Russia straddles both camps like no other. As part of the P5+1, it has joined in ever-increasing sanctions on Iran. Yet it also built Iran's only nuclear power reactor, and sold sophisticated armaments to Iran for years.
Like all the members of the P5+1, Russia does not want Iran to have a nuclear weapon. But it argues that diplomacy is the only way to ensure that end. So Russia's pessimistic assessment may matter, because of the wide chasm that remains as experts gather for technical meetings in Istanbul on July 3.
"For Russia the result is moderately positive," says Sergei Markov, a Kremlin adviser and vice president of the Plekhanov Economic University in Moscow. "It showed Iran is more ready to express its views and compromise, and the Western side did not issue an ultimatum."
Yet the talks need a "more clear advance and quicker developments" if they are to forestall a conflict, says Mr. Markov, who calculates that there is a "quite high" chance of an Israeli attack on Iran in July or August – just months before the US presidential election in November.
"If we would have three more years of such moderately positive results, it would be good," says Markov. "But in this much tighter time-frame, it is not enough."
Israel has repeatedly threatened military action to prevent Iran from achieving even the capability of making a nuclear weapon, much less an actual bomb, and demands that Iran halt all enrichment, permanently. It has decried the talks as a waste of time, while Iran continues to enrich uranium for what it declares are peaceful purposes.
Iran has repeatedly rejected nuclear weapons as un-Islamic, and US intelligence agencies believe that Iran has not made a decision to go for a bomb. Even if it did so, experts agree, Iran is still years away from making a deliverable device.