China on Friday imposed a levy on imports of an acid from the United States widely used in food, feed, pesticides and medical fields, amid heightened tensions with Washington over bilateral trade.

From Saturday, imports of propionic acid from the United States will be subject to a levy of 43.5%, the Ministry of Commerce said in a statement, after a July investigation found the Chinese domestic propionic acid industry was “materially damaged.”

A trade dispute between the world’s two biggest economies has been intensifying despite recent diplomatic visits.

In a recent salvo, the U.S. threatened to hike its tariffs on Chinese steel imports, and it is pressuring Mexico to prohibit China from selling its metal products to the U.S. indirectly from there.

China’s commerce ministry said Thursday said it firmly objects to the U.S. raising tariffs and will take all necessary measures to protect its rights and interests.