President Donald Trump on Thursday threatened to impose a massive tariff on European alcohol in response to the European Union’s retaliation against his steel and aluminum tariffs – a tit-for-tat escalation of a trade war that could easily get out of hand.

The president said he would impose the levies if the European Union did not walk back plans to place retaliatory tariffs on whiskey and other U.S. products.

Trump said he would impose the tariff if the European Union continues with its plan to impose a 50% tariff on whiskey beginning in April.