A 25% U.S. tariff on almost all goods imported from Canada and Mexico took effect Tuesday just after midnight, along with an additional 10% tariff on goods from China. The three countries together accounted for more than 40% of total U.S. imports last year and are also the top three U.S. export markets.

China will impose additional tariffs of up to 15% on some U.S. goods, its government said, while Canada vowed tariffs of up to 25%. Mexican President Claudia Sheinbaum announced her country would enact countermeasures Sunday in response to the U.S. tariffs, adding that they would include both “tariff and nontariff measures.”

The new Chinese levies, which take effect on March 10, include a 15% tariff on chicken, wheat, corn and cotton and a 10% tariff on sorghum, soybeans, pork, beef, fruits, vegetables and dairy and fish products. Chinese state media had reported earlier that U.S. agricultural products would be targeted.

China says that the U.S. tariffs undermine cooperation between the world’s two largest economies and that they hurt American businesses and consumers, as well as international trade.