The European Union’s executive branch has vowed to “take firm and immediate action” against U.S. President Donald Trump’s imposition of tariffs on steel and aluminum.

European Commission President Ursula von der Leyen said during the Munich security conference Friday the European Union will respond if the United States imposes reciprocal tariffs.

The commission’s response comes after Trump instructed staff to create tariffs on countries he sees as having unfair trade policies with the U.S.