Iran's nuclear weapons ambitions were discussed during the recent summit in Moscow between U.S. President Barack Obama and his Russian counterpart, Dmitri Medvedev.
The United States and the European Union believe Iran's uranium enrichment program is designed ultimately to build nuclear arms. Tehran says it only wants to use its enriched uranium for peaceful purposes, such as generating electricity.
In an effort to counter potential threats from countries such as Iran, the Bush administration proposed a missile defense system made up of 10 missile interceptors in Poland and a radar facility in the Czech Republic. President Obama is more cautious about the project and his administration is in the process of reviewing it.
Russian officials have been strongly critical of the proposal, saying it is targeted against Moscow - a view rejected by Washington. Moscow also sees the missile defense system as the first step in a worldwide American missile-defense program.
Iran's nuclear program and the missile defense issue were discussed during the recent Moscow summit. But presidents Obama and Medvedev disclosed very little about the nature of their discussions. One of the key disagreements is that Russia sees Iran as less of a threat than Washington does.
Analysts such as Steve Adreasen from the University of Minnesota say the summit final documents suggest Iran was addressed in the broadest terms.
"In the context of the missile defense joint statement, for example, although Iran isn't mentioned, there's a sentence at the end saying that the two presidents 'call upon all countries having a missile potential to refrain from steps that could lead to missile proliferation and undermine regional and global stability.' And although countries are not named in that statement, clearly there are two obvious candidates to whom that language might apply to - and they are North Korea and Iran," he said.
Many experts say whether Tehran decides to curtail its nuclear weapons ambitions could hinge on how much pressure Russia exerts on Tehran.
On the economic front, Russia is one of Iran's largest trading partners. It is building a nuclear power plant at Bushehr and it provides Tehran with consumer goods and weapons.
Former senior State Department official David Kramer, now with the German Marshall Fund in the United States, says several years ago, Tehran and Moscow signed an agreement for Russia to sell its sophisticated S-300 anti-missile defense system to Iran.
"I do worry about the possibility these missiles would be transferred. It has not happened since the deal was stuck, but I think there is a distinct possibility that it will. If Russia were to transfer these missiles, I worry very much about the possibility of an Israeli strike before these missiles were operable in Iran. And that, needless to say, would change the dynamics in the Middle East significantly," he said.
On the diplomatic front, Moscow, as well as Beijing, have been strong supporters of Iran. Both countries have also played a placating role at the United Nations Security Council
"Both Russia and China have signed on to resolutions condemning the movement on the part of Iran toward a nuclear weapons capability. They haven't backed it up with sufficiently strong action. And I think that as long as Iran believes, is convinced, it can separate the U.N. Security Council and divide that council so that Russia and China continue to lend support either moral or materiel, then we're not going to see a successful cessation of that program - at least through diplomatic means," he said.
Cohen says the Russians are key in preventing Iran from having a nuclear weapons program. "Unless they are actively engaged and are willing to commit to that, then I don't see a peaceful resolution of that issue. And I think most people look at that whole situation in the Middle East as being very volatile and don't want to see military action taken. But frankly, we've already seen discussions about Israel and I know that Israel is concerned about Iran - as are other countries in the region - very concerned about Iran possessing a nuclear weapon. Diplomacy is key and Russia is going to be key to achieving that diplomatically," he said.
However David Kramer says Russia's influence over Iran is limited. "I am not optimistic that we will get Russia on board in dealing with Iran. Russia really is not interested in applying pressure to the regime in Tehran - they'd rather have the United States and other countries do that. Russia has other interests in Iran. It has a different perception of the threat, although there were some indications coming out of the summit that there was a narrowing of those different perceptions. I'll believe it when I see it," he said.
Kramer and others point out that President Obama made scant reference to Iran during the final summit news conference - President Medvedev did not even mention it. That, says Kramer, suggests there are still significant differences between Washington and Moscow on how to deal with Tehran.