"We are categorically against use of force on this question and all our work will be based on this," Sergei Kislyak said on Friday.
"We consider a military conflict inadmissable and no military measures can resolve the non-proliferation problems of Iran."
The United States has repeatedly raised the possibility of using military means to pressure Iran into giving up its nuclear activity, which Western capitals claim consists of a secret bomb-making project hidden behind a civilian power programme.
On April 28 the UN Security Council will examine whether Iran has met a deadline for it to halt uranium enrichment work and to fully cooperate with inspectors from the Vienna-based IAEA.
Russia is Iran's chief partner in the civilian nuclear sphere and is building the Islamic republic's first nuclear power plant at Bushehr. Moscow this week also rejected Washington's calls for the Bushehr project to be halted.
Iran says that its only goal is to master nuclear technology and provide cheap electricity.