President Donald Trump said Tuesday that he is not bluffing about the possibility of slapping tariffs on European cars.

"They know that I'm going to put tariffs on them if they don't make a deal that's a fair deal," the president told The Wall Street Journal about ongoing trade negotiations with the European Union.

Trump's threat to put tariffs on a key European export — and once again ratchet up trade tensions with the economic bloc — has sparked backlash from European officials and companies. The White House has repeatedly delayed a decision on whether to put tariffs on cars from Europe. Trump did not reveal to the newspaper a deadline for his tariff decision.

The president made the comments Tuesday as government and business figures including German Chancellor Angela Merkel and European Commission President Ursula von der Leyen gathered at the World Economic Forum in Davos, Switzerland. Trump met with von der Leyen on Tuesday after speaking to the Journal.