European Commission President Ursula von der Leyen pledged on Tuesday a “firm and proportional” response from Europeans following U.S. President Donald Trump’s decision to impose tariffs on steel and aluminum.

In a statement, von der Leyen emphasized that the “unjustified” tariffs imposed on the European Union would not go unanswered, stressing the need for countermeasures.

Trump signed a decree imposing a 25% tariff on all steel and aluminum imports into the U.S. on March 12, raising widespread concern in European circles.