The US activated the Aegis missile defence system in Romania on 12 May 2016. The land-based Aegis ballistic missile defence system is equipped with long-range radar, and Standard Missile(SM)-3, which can intercept missiles and eliminate them, when airborne. The defense system was devised by the ex-US President George Bush. Later, the missile defense system was realised by Barack Obama in 2009. Phase II – construction in Romania was started in 2013. Construction of phase III site has also begun in Poland on the day after launch of the Romanian systems. In Poland it is scheduled to be completed in 2018.The activation of defense system in Europe has increased complications in Russia’s relations with NATO. The defence system has been observed by Russia as a threat to its national security. The Russian Military Doctrine 2014 explicitly notes ‘creation and deployment strategic systems’ of missile defence is major external threat to Russian Federation. The missile defence would undermine not only global stability, but also violates ‘the balance of forces in nuclear-missile sphere.’ Russia thinks it as a wider strategic programme of the US and it would affect the balance of the region. It has repeatedly raised objections to military escalation in its ICWA. More recently, Russian Prime said at the Munich conference of 2016 that NATO’s policy towards Russia is “unfriendly and generally obdurate.” He stated that Russia and the West are moving towards a “new cold war”, and Russia is being considered as the greatest threat to NATO and its allies. Various apparatus of addressing the concerns have died out and partnership initiatives are ending steadily.The NATO claims that the missile defense system is required to prevent hostilities against its allies from missile threats from outside the Euro-Atlantic space. According to the US as long as Iran keeps developing such missiles, the US will look out for its allies. Officials from the US and NATO state that the defense system is not targeting Russia. They talked about the Iranian missile programme. Jens Stoltenberg stated that the objective of NATO is to achieve complete coverage and protection for European Allies against ballistic missile attacks from outside the Euro-Atlantic area. Both put forward the argument that SM-3 could not change the strategic balance of the region because the missiles cannot intercept Russian intercontinental ballistic missiles (ICBMs) and do not carry any explosives. Technically these missiles are designed to destroy high-velocity targets by hitting them head-on. Russia was also assured that nuclear capable missiles will not be placed in the Romanian base.The construction of the defense site in Romania did not surprise Russia. Russia claims that it would fuel an arms race in the area.Thus, Russia will not stop re-arming its forces. Russia criticized NATO for the use of the Iran programme as an excuse to deploy the defense system in Europe. These missiles cannot reach any territory belonging to Europe. Iran has already signed the nuclear agreement with the P5 plus Germany in July of 2015. Russia blames the US for stepping up the military build-up on its borders in order to surround it. It voiced complaints over the installation of SPY-1 radars in the Romania site, which can be utilised for spying on missile tests. The Romanian system can also be re-equipped with offensive missiles.