Last month, Russian Prime Minister Dmitry Medvedev, speaking at the World Economic Forum in Switzerland, said efforts to advance a customs union with former Soviet republics didn't equate to an about-face on Kremlin policy.
U.S. missile defense plans in Eastern Europe prompted Moscow to call for assurances the program wouldn't target its strategic interests.
Putin told the Russian Defense Ministry there were "systematic attempts" at undermining Russia's sphere of influence.
"In fact, the second stage of the U.S. global missile defense system is being launched, and the possibilities for further NATO eastward expansion are being explored," he was quoted by state-owned news agency RIA Novosti as saying. "The danger of the militarization of the arctic also persists."
Israel tested a weapons system this week with the help of the U.S. Missile Defense Agency. The system is meant to counter Iranian missile threats. Washington said its missile plans for Europe are designed to deter Iranian and North Korean threats.