The U.S. Navy and Coast Guard say Russia is strengthening its military forces in the Arctic Ocean.
The deployment of ships, warplanes and troops is part of Russia's bid to secure its northern coast and open a shipping route from Asia to Europe now more accessible to ships because of international warming.
Satellite images show the buildup and flow of weapons and troops to the country's Arctic coastline. They also confirm a strengthening of airfields.
The U.S. Department of Defense sees this as a bid to establish de facto Russian control over areas of the Arctic.
Russian bases are meant to deny others access to mineral rich areas and cement national control over these locations.
Russia plans to build four bases at Rogachevo, Cape Schmidt, Wrangel and Sredniy.
"Russia is refurbishing Soviet-era airfields and radar installations, constructing new ports and search-and-rescue centers, and building up its fleet of nuclear- and conventionally-powered icebreakers," said Lt. Col. Thomas Campbell, a Pentagon spokesman.
"It is also expanding its network of air and coastal defense missile systems, thus strengthening its anti-access and area-denial capabilities over key portions of the Arctic."
The Pentagon is anxious about Russia's moves to influence the northern sea route - the shipping lane between Norway and Alaska along Russia's northern coast. The route halves the time it currently takes shipping containers to reach Europe from Asia via the Suez Canal.
Campbell said Russia wanted to exert control over the route and said the Pentagon was concerned at the rules Russia wants to impose on ships transiting the seaway.
"They require any vessel transiting the route through international waters to have a Russian pilot...Russia is also attempting to require foreign vessels to obtain permission before entering."
