Russia on Tuesday warned the United States against sending a ballistic missile defense system to South Korea, saying it could threaten regional security.
Washington says it wants to deploy the system, known as THAAD, to South Korea as a deterrent to military provocation by North Korea.
"Such a development cannot but cause concern about the destructive influence of the United States' global missile defense on international security," Russia's foreign ministry said in a statement.
"In a region where the situation is already extremely complicated in terms of security, this could serve as another push toward an arms race in northeast Asia and further complicate any resolution of the nuclear issues on the Korean peninsula," the statement said.
China has also already warned that deployment of the system would undermine peace and stability in the region.
Faced with growing isolation from the West over the Ukraine crisis, Russia has moved to bolster ties with former Cold War-ally North Korea.
Moscow and Pyongyang have named 2015 a "year of friendship" between the two countries and the Kremlin says reclusive leader Kim Jong-Un is set to make his first official trip abroad to visit Russia's World War Two victory commemoration in May.
South Korea and the United States will launch a massive landing drill March 28 as the climax of an ongoing joint military exercise which North Korea views as an invasion rehearsal.