But has the Su-57 made its debut in Syria? The Pentagon, won't confirm it.
The Kremlin denied involvement in air strikes on Syria's Eastern Ghouta enclave that have killed at least 250 civilians.
Russia admitted Tuesday that several dozen of its "citizens" had been killed or wounded in recent fighting in Syria.
The disappearance of the ice pack has made Arctic passages potentially viable alternatives to existing routes.
The USS Ross and USS Carney are patrolling the sea to help maintain regional security and stability, the Navy said.
The evidence describes a vast, secret, social-media campaign financed by a Russian entrepreneur.
Thirteen Russians and three Russian entities were charged with an plot to interfere in the 2016 U.S. presidential election.
Russia acknowledged Thursday that five of its citizens may have been killed by a U.S. strike in Syria.
U.S. officials said they had no information on such casualties, and the Kremlin did not confirm any Russian deaths.
A U.S. MQ-9 Reaper drone took out a Soviet-made T-72 tank in eastern Syria on Saturday in a "self-defense" strike..