"From Switzerland's point of view, the additional duties, which according to the U.S. have been introduced to protect national security, are unjustified," the statement from the Swiss economy ministry said in a statement.

Under WTO rules, the United States has 60 days to settle the issue. After that time, Switzerland could escalate the dispute by asking the WTO to set up a panel of judges to adjudicate.

(Reporting by Tom Miles; editing by John Stonestreet)