Vladimir Putin has warned that Russia is set to move some of its missiles closer to Europe in response to NATO "expansion" plans.
Russia is to deploy its S-400 air missile defence system and ballistic Iskander missile in the Kaliningrad region - which is separated from the Russian mainland by borders with Poland and Lithuania.
In a television interview due for broadcast later today, Mr Putin said he is “concerned by NATO’s decision making.”
Vikto Ozerov, head of the Russian defence committee, told Russian media sources the deployment is in response to the US setting up a missile shield in Europe.
NATO Secretary General, Jens Stoltenberg said the alliance aims to, “prevent a conflict, not to provoke a conflict.”
"Everything NATO does is defensive, proportionate and fully in line with our international commitments,” he said.
"Before Russia's aggressive actions in Ukraine, NATO had no plans to send troops to the Eastern part of our alliance.
He said NATO is “firmly committed” to a two-track approach to international relations with Russia - “strong defence, coupled with meaningful dialogue."
US President Barack Obama met with Mr Putin in Peru on Sunday, with the pair discussing the ongoing situation in Ukraine and Syria.
Mr Obama encouraged his Russian counterpart to stand by an agreement made in Minsk that was aimed at ending the Ukraine conflict.
He also called for US Secretary of State John Kerry and Russia's Foreign Minister Sergei Lavrov to continue working with other countries to solve the war in Syria.
Mr Putin said that that both leaders had acknowledged that dialogue between their countries "was hard" but said he would be happy to see the outgoing US President in Russia.
He also spoke of Mr Obama's successor Donald Trump, saying the two men share an interest in "normalising relations."
He said there was a big difference between Mr Trump’s “pre-election rhetoric and actual policy."