WASHINGTON (Reuters) -U.S. President Donald Trump on Friday said he had ordered two nuclear submarines to be positioned in "the appropriate regions" in response to remarks from former Russian President Dmitry Medvedev about the risk of war between the nuclear-armed adversaries.

Russian officials claimed their own nuclear fleet is more than capable of countering American maneuvers. The move has sparked concern globally, but Moscow insists there is no need for retaliation - yet.