Russian President Vladimir Putin on Monday accused the West of pushing Russia to its "red lines" - situations it has publicly made clear it will not tolerate - and said Moscow had been forced to respond.
Putin told a meeting of defense officials that Russia was watching the US development and potential deployment of short and medium-range missiles with concern.
He said Russia would lift all of its own voluntary restrictions on the deployment of its own missiles if the US went ahead and deployed such missiles.
Putin, who said Russian forces in Ukraine have taken control of 189 settlements so far this year, said Russia's nuclear weapons were there for deterrence.