Several countries - including Russia - are reviewing their co-operation with Iran in light of the looming UN sanctions.
Russia signed a deal in 2007 to supply Iran with the advanced, long-range air defence system, the S-300, but so far nothing's been delivered.
The agreement's believed to be worth around $1 billion.
Officials had hinted that the S-300 is not subject to the new sanctions because it's a purely defensive weapon.
Now, Foreign Minister Sergey Lavrov says any future course of action is President Medvedev’s call.
“We should take into account that the resolution includes a whole set of measures, which cover different aspects of relations with Iran and other countries and they are all inter-connected. According to our practice, a UN Security Council's resolution must first be realised through a decree of the Russian president before it is implemented, as will be done in this case. The resolution will define which particular arms are to be banned from being supplied to Iran according to the resolution,” Lavrov said.
Russia also says the new restrictions will not affect construction of the Bushehr nuclear power plant – which is expected to power up in August.
But analysts such as Ruslan Pukhov from the Moscow-based Centre for Analysis of Strategies and Technologies believe Russia's paying the price for its reinvigorated friendship with the US
“We are supposed to return the advance payment and we will be sanctioned by Iran," Pukhov told RT. "Our direct financial losses will be $1 billion right now; and in long term we face another $2-billion-worth of unsigned contracts. So the friendship with the U.S. and President Obama will cost us a lot”.