SEOUL, April 14 (Reuters) - North Korea's military said on Friday it would "ruthlessly ravage" the United States if Washington chose to attack, as a U.S. aircraft carrier group headed for the region amid fears the North may conduct a sixth nuclear weapons test. "Our toughest counteraction against the U.S. and its vassal forces will be taken in such a merciless manner as not to allow the aggressors to survive," North Korea's official KCNA news agency quoted its military as saying in a statement.
