European Union officials are priming their regulatory guns to fire back at U.S. President Donald Trump’s tariff plan.

EU leaders on Wednesday were discussing possible responses to the Trump administration’s proposal to impose tariffs on steel and aluminum imports.

European Commission President Jean-Claude Juncker offered this comment in recent days, according to multiple published reports.

“ ‘This is basically a stupid process, the fact that we have to do this. But we have to do it. ... We can also do stupid.’ ” — European Commission President Jean-Claude Juncker on responding to Trump’s tariff plan

On Wednesday, an EU official in charge of trade policy — Cecilia Malmström — added to the blunt talk from the trade bloc.

She said: “We have made it clear that a move that hurts the EU and puts thousands of European jobs in jeopardy will be met with a firm and proportionate response.”

The EU could impose levies totaling $3.5 billion on U.S. agriculture, steel and industrial products, as well as iconic American products such as Harley-Davidson HOG, -3.84% motorcycles, according to a Wall Street Journal report.

A similar approach was successful in a trade fight with former President George W. Bush, the Journal report noted.

See:Trump tariffs may really be a backdoor way to get out of the WTO

And read:Why a full-blown Trump trade war won’t happen

Trump hasn’t shown signs of backing down. He tweeted Saturday that he would consider a tax on imported cars if European leaders increased tariffs on U.S. goods.

Concerns about a possible global trade war have been intensifying due to Trump’s plan to introduce tariffs on steel and aluminum imports and due to the resignation Tuesday of Gary Cohn, who had been a pro-trade White House adviser. The Trump administration is reportedly mulling a broad range of import tariffs on Chinese goods. U.S. stock futures US:ESH8 were trading sharply lower early Wednesday.

Don’t miss:How a tariff-rattled stock market is reacting to Cohn’s resignation

And see:Meet Peter Navarro, the man who pushed Cohn out