Russian Deputy Foreign Minister Sergei Ryabkov made the remarks on Saturday at an international nuclear weapons non-proliferation conference , TASS reported.
Russia is not ready to participate in any talks on amending the Joint Comprehensive Plan of Action (JCPOA), Ryabkov said.
The deal is delicately balanced and any change could cause the collapse of the whole agreement, he warned.
The JCPOA was reached between Iran, the five permanent members of the United Nations Security Council — Britain, China, France, Russia and the United States — plus Germany, in July 2015. Under the deal, Iran agreed to halt its nuclear weapon programme in exchange for economic aid and lifting of international sanctions.
However, on October 13, US President Donald Trump called for decertifying the agreement, alleging Iran had committed "multiple violations".
Though the decertification would not mean Washington exiting the Iran nuclear deal at the moment, it would open a 60-day window in which the US Congress could reimpose nuclear-related sanctions on Iran.
International Atomic Energy Agency Director General Yukiya Amano said last week that Iran was implementing the JCPOA under a robust verification regime.