The European Commission has confirmed import duties of 25% will be applied to US steel, aluminium and other products from Friday.
The measures target a list of products, including agricultural goods, worth €2.8 billion (£2.5bn).
The retaliatory tariffs are in response to steel and aluminium import duties imposed by US President Donald Trump earlier this month, which are worth a total of €6.4 billion (£5.6bn).
EU Commissioner for Trade Cecilia Malmstrom said: “We did not want to be in this position. However, the unilateral and unjustified decision of the US to impose steel and aluminium tariffs on the EU means that we are left with no other choice.
“The rules of international trade, which we have developed over the years hand in hand with our American partners, cannot be violated without a reaction from our side… Needless to say, if the US removes its tariffs, our measures will also be removed.”
The UK Government added the nation’s steel and aluminium products are important for US businesses and defence and it “rejects any claim that they harm US national security”.
A spokesperson said: “The EU rebalancing plans are a measured and proportionate response which we support. We will maintain our dialogue with the Commission on the products listed. We will also continue to seek a constructive resolution with the US to avoid further escalation that would harm businesses and consumers in both the US and EU.”