President Donald Trump imposed steep tariffs on imported solar cells on Monday in response to a trade case brought by U.S. solar manufacturers charging that cheap imports, particularly from China, were harming domestic solar companies.

The United States trade representative, Robert Lighthizer, announced that the president had decided to impose the tariffs, accepting the recommendation of the administration’s trade advisors. The United States International Trade Commission, an independent body of trade experts, had engaged in “an exhaustive process” to examine the charges filed by American businesses and concluded that U.S. producers had been “seriously injured” by imports.

“The President’s action makes clear again that the Trump Administration will always defend American workers, farmers, ranchers, and businesses,” Lighthizer said.

A tariff of 30 percent will be levied on imported solar modules and cells in the first year. That will decline to 25 percent in the second year, 20 percent in the third year, and 15 percent in the fourth year.

The Trump administration is also imposing tariffs and a quota on importing washing machines following a trade commission investigation. In the first year, the first 1.2 million washing machines that are imported will face a 20 percent tariff, while all subsequent imports will face a 50 percent tariff.