Medvedev said the new facility should be viewed by the West as the "first signal" of Russia's readiness to counter threats posed by NATO's missile defense plans, the Russian news agency RIA Novosti reported.
The radar station is in Kaliningrad at Russia's western-most border.
"If our signal is not heard, as I said on Nov. 23, we will continue deploying other defense means," Medvedev said.
Moscow is seeking written, legally binding guarantees that the U.S.-led European missile defense shield will not be directed against Russia.
"We can no longer be satisfied with a common statement that the phased and adaptive (missile defense) system that is being created is not directed against Russia, Medvedev said. "Those are empty words, which unfortunately do not guarantee the protection of our interests."