"Now that these anti-missile elements have been installed we will be forced to consider putting an end to the threats emerging in relation to Russia's security," Putin said during a meeting with military officials on Friday.
He also stressed that Moscow is doing its best to sustain strategic balance of power.
"Of course, we are doing everything needed from our side so as to provide for the maintenance of this strategic balance of power that is the most reliable guarantee against the appearance of large-scale military conflicts," Putin said.
However, he noted that his country will not be involved in any arms race.
The Russian president also described the US deployment of the missile system as an attempt by Washington to increase its nuclear potential, adding that the complex deployed in Poland near Russia may be easily used for firing short- and mid-range missiles.
He also condemned the deployment as a clear violation of arms treaties signed between Russia and the US, adding that it would escalate international tensions.
Putin also criticized Washington for ignoring Russia's concerns and rejecting Moscow’s calls for cooperation on the issue.
"All our proposals were rejected, we are invited not to jointly work, but to discuss this issue, nothing concrete. Everything is done unilaterally, without taking into account our concerns."
On Thursday, officials from the US and the Western military alliance of NATO declared the missile system based in southern Romania operational. The missiles’ activation marked the penultimate step in the completion of a so-called missile shield, which Washington proposed nearly a decade ago.
The United States will break ground on the final site in Poland on Friday. Upon completion in late 2018, the umbrella would be stretching from Greenland to the Azores region in western Portugal.
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