BRUSSEL - The European Union (EU) will trigger a dispute settlement case at the World Trade Organization (WTO), since US restrictions on steel and aluminum "clearly go against" agreed international rules, EU officials said on Thursday.

"The EU believes these unilateral US tariffs are unjustified and at odds with WTO rules. This is protectionism, pure and simple," Jean-Claude Juncker, president of the European Commission, said in a statement.

"The United States has sought to use the threat of trade restrictions as leverage to obtain concessions from the EU. This is not the way we do business, and certainly not between longstanding partners, friends and allies," EU Trade Commissioner Cecilia Malmstrom said in a statement.

"Now that we have clarity, the EU's response will be proportionate and in accordance with WTO rules. We will now trigger a dispute settlement case at the WTO, since these US measures clearly go against agreed international rules," she said.

"We will also impose rebalancing measures and take any necessary steps to protect the EU market from trade diversion caused by these US restrictions," she added.

The EU will use the possibility under WTO rules to rebalance the situation by targeting a list of U.S. products with additional duties, and the level of tariffs to be applied will reflect the damage caused by the new US trade restrictions on EU products, the EU statement added.

According to the EU, the US measures affect EU exports worth 6.4 billion euros (7.46 billion U.S. dollars) in 2017.

"While striving to avoid today's situation, the EU has been preparing over the last months and stands now ready to react to the US trade restrictions on steel and aluminum in a swift, firm, proportionate and fully WTO-compatible manner," the EU added in a statement.