The US administration insists that the system is designed to counter threats from Iran, but its continued refusal to accept Russian offers of cooperation has reinforced widespread views that Russia is actually the target. There is no mention of missile defence systems in the Treaty, but the US reserves the right to develop the system, and Russia reserves the right to pull out of the Treaty if it thinks US missile defence is threatening its security.
NATO has now entered the fray. At its summit in November, it agreed to adopt the US missile defence system in Europe as a NATO project. President Medvedev is not happy. The day before the Treaty vote, he announced that Russia would deploy its own missile defence system and adopt a more offensive nuclear posture, to secure adequate protection for Russia, if it were not given an equal role in the NATO system.
Clearly, missile defence continues to have the potential to restart the nuclear arms race of the past. It remains a highly destabilising concept. The great danger is that US insistence on its development will prevent any further progress on nuclear disarmament.