Russia has accused the West of encroaching on its borders, forcing Moscow to take measures to "safeguard its own interests".
"It's not Russia that's approaching someone's borders. It's Nato's military infrastructure that is approaching the borders of Russia," Kremlin spokesman Dmitry Peskov told reporters. "All this... forces Russia to take measures to safeguard its own interests, its own security."
The remarks come after the country's president, Vladimir Putin, announced on 16 June that Russia would boost its nuclear arsenal with 40 new missiles.
Earlier in the week, the US reported plans to place heavy military equipment in Eastern European Nato states. Yuri Ushakov, foreign policy aide to Putin, told reporters on 17 June that Russia did not want an arms race.
"We are against any arms race because it naturally weakens our economic capabilities. And in principle we are against it," he said at a briefing.
Tensions between Russia and the West are currently at their highest point since the Cold War, with Moscow charged with supplying troops and arms to separatist militants in east Ukraine, claims it denies.