European Commission President Ursula von der Leyen vowed "firm and proportionate countermeasures" in response to U.S. President’s decision to impose tariffs on all steel and aluminium imports, escalating fears of a trade war, writes Reuters.

“I deeply regret the US decision. Unjustified tariffs on the EU will not go unanswered – they will trigger firm and proportionate countermeasures in response”, - added Ursula von der Leyen.

Donald Trump signed proclamations late on Monday, February, 10, to raise tariffs on all steel and aluminium imports to 25% without exceptions or exemptions.

A White House official said that the measures would take effect on March 4.