The trade threats could reduce exports to the United States and dampen investment in Europe, dealing a blow to growth at a time when the continent is already facing a lackluster economy.

The European Commission said on Friday it would react "firmly and immediately" against tariff increases resulting from U.S. President Donald Trump's proposed reciprocal trade policy, which it labelled unjustified and a step in the wrong direction.

Over $600 billion in European goods were imported by the U.S. last year. New tariffs from President Trump will likely hit these popular categories the hardest.