President Donald Trump says he is serious about potentially slapping European cars with tariffs as trade negotiations between the U.S. and Europe continue.

CNBC reports that Trump’s threat of tariffs has sparked backlash from European officials and companies. The president hasn’t revealed a deadline for his tariff decision but has been considering such a move for many months.

Last week, Trump threatened European cars with a 25 per cent tariff if Britain, Germany, and France did not accuse Iran of breaking the terms of the 2015 nuclear deal. The president made his latest comments earlier this week speaking at the World Economic Forum in Davos, Switzerland.

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“They know that I’m going to put tariffs on them if they don’t make a deal that’s a fair deal,” he told The Wall Street Journal.

Late last year, the U.S. let a previous deadline of November 13 for the introduction of auto tariffs lapse. At the time, former European Trade Commissioner Cecilia Malmstrom said the EU considered this an indication from Trump that tariffs would not be introduced.

President Trump recently reached an agreement with French President Emmanuel Macron to postpone a tax France will levy on big tech companies until the end of 2020. A number of other bilateral meetings are planned for the event in Switzerland and will provide the president with the opportunity to discuss a new trade deal with Europe.