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.

Trump said he would up the ante after the E.U. imposed its own 50% tax on American whiskey, a move that itself was a response to the White House tariff on European steel and aluminum.