TEHRAN - Mikhail Ulyanov, Russia's permanent representative to the Vienna-based international organizations, has responded to Western calls to improve a 2015 nuclear deal between Iran and world powers.

“Some analysts advocate for a ‘better deal with Iran’. They forgot that the perfect is the enemy of the good. The return to the original deal is by itself a big challenge. Any attempt “to improve” it would require years of negotiations without any guarantee of positive result,” the Russian diplomat said in a tweet on Sunday.

Ulyanov’s tweet seems to have been published to recent remarks by some European officials and pundits about what they call the need to improve the Iran nuclear deal from which Donald Trump withdrew more than two years ago.

Joe Biden has vowed to rejoin the nuclear deal.

However, European signatories to the deal – officially known as the Joint Comprehensive Plan of Action (JCPOA) – have publicly called for expanding it in a way that includes Iran’s defensive missile program and its regional influence.

German Foreign Minister Heiko Maas has explicitly pushed for such a deal in his recent interview with Der Spiegel.

“A return to the previous agreement will not suffice anyway. There will have to be a kind of ‘nuclear agreement plus,’ which is also in our interest. We have clear expectations of Iran: no nuclear weapons, but also no ballistic missile program that threatens the entire region. Iran also needs to play a different role in the region,” Maas told the German magazine, adding, “We need this agreement precisely because we distrust Iran. I have already coordinated with my French and British counterparts on this.”