Moscow: President Vladimir Putin on Friday warned that Russia would consider measures to "end threats" from US anti-missile systems in Europe but said Moscow would not engage in a new arms race.
"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 told defence officials in televised remarks.
Putin spoke after a US anti-missile defence system in Romania aimed at protecting NATO members from threats by "rogue" nations became operational on Thursday.
The anti-missile defence system in Romania is part of a broader NATO missile shield to include an installation in Poland, work on which was set to begin on Friday.
Referring also to the placing of the Aegis missile defence system on warships in the Mediterranean, Putin said: "All of these are additional steps towards destabilising the international security system and the start of a new arms race."
The Russian president said the United States violated the Intermediate-Range Nuclear Forces Treaty (INF) signed by Mikhail Gorbachev and Ronald Reagan in 1987, adding that the US sites in Europe could be used to launch intermediate-range and shorter-range missiles.
Work on the sites is happening at a brisk pace and Russia is unable to control what is happening there, Putin said. "And this is an additional threat for us," he added.
Putin insisted that Russia would seek to maintain a strategic balance but at the same time would not allow itself to get sucked into a new arms race.
"We will not be involved in this race, we will go our own way, we will work very carefully," he said.
Located in Deveselu in southern Romania, the US missile interceptor station will help defend NATO members against the threat of short- and medium-range ballistic missiles, particularly from the Middle East, officials say.
But Russia sees the missile system as a security threat right on its doorstep, despite the US and NATO insisting it is not aimed at undermining Moscow's defences.