Lavrov said that the nuclear talks have covered most issues and "from our point of view, if Iran agrees, this document can already be launched into the acceptance process".

But he added that there are "problems that have appeared recently from the point of view of Russia's interests", due to concerns over the terms of the deal concerning Moscow's involvement in the civilian nuclear sector in Iran and arms sales to Tehran.

Lavrov cited the "avalanche of aggressive sanctions that the West has started spewing out, which hasn't ended as far as I understand", over the Ukraine conflict.

He said this meant Moscow had to ask the US for guarantees first, requiring a "clear answer" that the new sanctions will not affect its rights under the nuclear deal.

"We requested that our US colleagues ... give us written guarantees at the minimum level of Secretary of State that the current (sanctions) process launched by the US will not in any way harm our right to free, fully-fledged trade and economic and investment cooperation and military-technical cooperation with Iran," Lavrov said at a news conference.