If the US followed through with threats to impose further harsh economic sanctions it would be seen as a "declaration of economic war," Hurriyet Daily News reported.
The warning by Prime Minister Dmitry Medvedev came after Washington unveiled a raft of new sanctions against Russia over its alleged use of the Novichok nerve agent against a former double agent which Britain has blamed on Moscow.
"While I don’t want to comment on the talk about future sanctions, I can say that if we end up with something like a ban on banking activities or the use of certain currencies, we can clearly call this a declaration of economic war," Medvedev was quoted as saying by the Interfax news agency.
"And we must absolutely respond to this war. By economic means, by political means and if necessary by other means," he added.
"Our American friends must understand this."