President Dmitry Medvedev renewed a threat on Friday to deploy missiles in Russia's exclave of Kaliningrad near Poland if Washington goes ahead with its missile shield plans in Europe.
"If we cannot agree on this question (missile defence) then you know the consequences," he told reporters after a G8 summit in L'Aquila, central Italy.
"I have nothing to add and what I said in my address to the nation remains valid."
Medvedev in his speech in November warned that Moscow would deploy missiles in Kaliningrad, a Russian territory wedged between Poland and Lithuania, if the United States pressed on with its missile defence plan.
In 2008, Poland and neighbouring Czech Republic signed preliminary agreements with then president George W Bush's administration to install missile silos and radar bases respectively on their soil.
Bush's successor Obama has launched a review of the controversial system but has nonetheless said Washington will move forward with the system as long as there is an Iranian missile threat.