Three of the five Security Council members -- France, the UK, and the US – which of course may have minor differences, are all united by their common membership in NATO, which has declared itself, among other things, as a “nuclear alliance”. A rising China, while participating fully in the P5+1 talks, has recently been more concerned with issues such as its own security in the Asia-Pacific region, developing geopolitical clout in Central Asia and increasing its investment posture in Africa. Russia, on the other hand, has deeply vested interests in the Middle East, and the pursuit of its own interests against the backdrop of the P5+1 dialogue has complicated things. Aside from the fact that Russia is a member of the UN Security Council and a declared nuclear state which recognizes the NPT, Russia also seeks to increase its influence in the Middle East. Russia, in fact, has already begun to overtake the US in the Middle East, at least in terms of prestige and influence. Russia enjoys much better ties with Iran than the US does, and as such may be in a better position to act as a catalyst for change, although, conversely, it could be a source of instability for the talks.
Last autumn, what seemed like a promising amount of progress in the negotiations with Iran fell through because of Russian objections. Many American analysts have asserted over the past few years that Russia enjoys being difficult for the sake of being difficult and to thwart American influence and prestige whenever possible. Allegedly, though, this was not the cause of Russian objections. After the failed talks with Iran, Russian foreign minister Sergei Lavrov stated that the US made last-minute amendments to the draft text without consulting Russia, which the Russian side found unacceptable. Given Russian desires to be seen as a major international actor, and its sensitivity to perceived diplomatic slights by the U.S., this bears some semblance to Russian protestations at being excluded from talks with East Asian regional powers over North Korea’s nuclear program (which eventually culminated in the now-suspended Six Party Talks). Russia’s objections had legitimate grounds, seeing as they were already a full-fledged, committed party to the Iranian talks.
Controversy has recently arisen over alleged Russian plans to purchase up to half a million barrels of oil from Iran per day. This has been linked to the Iran nuclear deal, in a way that would undermine talks. While this has not been definitively confirmed, many fear that if Iran is able to sell oil to Russia, it will undercut the leverage over Iran that has resulted from sanctions. While there may be some connection between Russian purchases of Iranian energy and the nuclear talks, these two issues should be kept separate by and large. However much this may (or may not) be true, this possible oil deal would likely be better understood in the context of the energy geopolitics of the Caspian Sea (a body of water surrounded by five major energy producing states, including Iran and Russia). Russia purchases energy from other Caspian and Central Asian states such as Turkmenistan at a discount, then repackages and sells it. This is probably what Russia plans to do with Iranian energy.
Russia, of course, has supported Iran's construction of a nuclear reactor. Russia also does not have sanctions against Iran to the extent of the US and EU, which gives Iran some wiggle room in terms of diplomatic and economic maneuvering.
Israeli Prime Minister Binyamin Netanyahu traveled to Russia to meet with Russian president Vladimir Putin to try and sway Russia's position away from a deal with Iran. This is no doubt based on two factors- the fact that Russia is one of Iran's stronger allies and that Israel's political culture has seen the rise of members of the country's large Russian-speaking population. Israel obviously recognizes Russia's pivotal importance in the talks and hopes to use the ties between Russia's Jewish population and Israel's own Russian-speakers to try and leverage influence on Russia's position. Israel's deputy foreign minister, Ze'ev Elkin (a Russian-speaker who was born in the former USSR), stated he did not think that Russia's position would change noticeably, but that any small budge in Israel's favor would be immensely helpful.
All of this serves as an excellent reminder that, while the Iranian nuclear issue is often portrayed in a somewhat bilateral manner (P5+1 on one side, Iran on the other, or perhaps even "Iran versus the world"), this is in fact a very multifaceted and complex issue which should be understood and approached from a foreign policy perspective which takes into consideration various sides. Our mutual cooperation is essential to ultimately seeing a peaceful and diplomatic solution to what is not a bilateral or even regional issue, but a worldwide affair.