Russia and NATO initially agreed to cooperate on the so-called European missile defense system at the Lisbon summit in November 2010. However, further talks between Russia and the alliance have floundered over NATO’s refusal to grant Russia legal guarantees that the system would not be aimed against Russia’s strategic nuclear deterrent.

NATO and the United States insist the shield is designed to defend NATO members against missiles from emerging threat nations like North Korea and Iran, and would not be directed at Russia. The alliance has vowed to continue developing and deploying its missile defenses, regardless of the status of missile defense cooperation with Russia.

The final phase of the so-called European Phased Adaptive Approach envisions the deployment of US SM-3 Block IIB interceptors by 2020 “to help better cope with medium- and intermediate-range missiles and the potential future ICBM threat to the United States.”

Russia has threatened a range of countermeasures against NATO's missile defenses, including tactical nuclear missile deployment in its Baltic exclave of Kaliningrad and improvements to its strategic nuclear missile arsenal.

Russia has invited US Joint Chiefs of Staff Chairman Martin Dempsey to Moscow for talks which will include the missile defense issue, his Russian counterpart Army General Valery Gerasimov said Wednesday.