U.S. President Donald Trump is reiterating his threat to impose tariffs on countries that treat the U.S. unfairly when it comes to trade.  

“Tariffs are the greatest!” Trump wrote in a Twitter post Tuesday, warning countries must negotiate a “fair” trade deal or they will get hit with tariffs.

 Trump’s message comes ahead of his meeting with European Commission President Jean-Claude Juncker in Washington, D.C. on Wednesday.

It also comes amid recent reports that Mexico is aiming to reach a deal on the North American Free Trade Agreement with the U.S. and Canada by the end of August to take some of the heat off incoming President Andres Manuel Lopez Obrador.