Citing a senior western diplomat, the Wall Street Journal reported that Russia's chief nuclear negotiator informed the EU it would accept narrower guarantees if it meant Moscow could carry out nuclear work with Iran under the 2015 agreement.

Such work includes a uranium swap with Iran, the redesign of the Fordow nuclear facility and the provision of nuclear fuel to Iranian reactors.

Barbara Slavin, the director of the Future of Iran Initiative at the Atlantic Council, told Middle East Eye that "basically, the Russians caved".

"What we've seen is the Russians have climbed down from Lavrov's demand a week or so ago that they had to have a free hand in trading with Iran," Slavin said.