President Trump threatened to impose tariffs on the European Union, in what would be an economic counter-strike to Europe’s expected response to impending steel tariffs.

“If the E.U. wants to further increase their already massive tariffs and barriers on U.S. companies doing business there, we will simply apply a Tax on their Cars which freely pour into the U.S,” the president tweeted Saturday afternoon.

Trump sparked contretemps Thursday by announcing a plan to impose tariffs on foreign steel and aluminum, which are designed to help the American steel industry by raising the price of foreign steel. EU officials have signaled for weeks that they would respond with tariffs on Harley-Davidson and Kentucky bourbon. Those are politically pointed choices, as the products are made in the respective home states of House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell.

"This is basically a stupid process, the fact that we have to do this,” European Commission President Jean-Claude Juncker said Friday evening. “But we have to do it. We will now impose tariffs on motorcycles, Harley Davidson, on blue jeans, Levis, on Bourbon. We can also do stupid. We also have to be this stupid.”

Trump’s retort takes aim at one of the crown jewels of Germany — the home of BMW, Mercedes, Volkswagen — which is Europe’s largest economy. “They make it impossible for our cars (and more) to sell there,” he wrote in the tweet. “Big trade imbalance!”

The European Union was the largest exporter of automobiles in 2016, according to EU data compiled in 2017. Japan was the second-largest exporter. The United States was the third-largest auto exporter in the world, but also imported more cars from the EU than any other country.

“When a country (USA) is losing many billions of dollars on trade with virtually every country it does business with, trade wars are good, and easy to win,” Trump tweeted Friday.