The Chinese government has filed a challenge to the tariffs on steel and aluminum imposed by the Trump administration.

The complaint, filed this week with the World Trade Organization in Geneva, says that the 25 percent tariff on imported steel and 10 percent levy on imports of aluminum were improper and not uniformly applied, since Canada, Mexico, the European Union and other key trading partners are exempt.

China has requested formal discussions with the U.S. on the matter. The trade fight could also go to a WTO panel.

President Donald Trump and some other countries have long complained that China “dumps” excess steel on the world market, depressing prices and costing jobs. China and the U.S. have threatened to slap tariffs on billions of dollars’ worth of each country’s goods, including HVAC equipment.