President Donald Trump lashed out at tariffs placed on American cars sold in China, saying the trade structure disproportionately hurts the U.S.

In a Twitter posting Monday morning, Trump said the current system levies a 2.5 percent tariff on every Chinese car imported to the U.S., while placing a 25 percent duty on cars going the other way. He assailed what he said has been an historic imbalance.

“Does that sound like free or fair trade. No, it sounds like STUPID TRADE - going on for years!” Trump said in the message.

To date, imports of Chinese-assembled cars into the U.S. have been small but growing.

Ford Motor Co. plans to begin importing Chinese-assembled versions of it Focus model to the U.S. next year. So far, Geely Automobiles Holding Ltd.-owned Volvo Cars started importing S60 sedans from China in 2015 and General Motors Co. has followed suit with the Buick Envision SUV and Cadillac CT6 plug-in hybrid.

Trade tensions between the two countries have intensified recently, roiling world markets. Trump in March ordered up tariffs on steel and aluminum imports and last week said the U.S. plans to review additional tariffs on China, retaliation for what he calls decades of intellectual property theft. China has responded with tariffs of its own on 106 products ranging from soybeans to aircraft and threatens more.