The Department of Commerce hit solar panels imported from China with a 30% tariff on Thursday. The government found that Chinese firms had been dumping solar panels on the U.S. market to the detriment of American manufacturers.

While a string of bankruptcies among U.S. solar panel makers had prompted considerable complaints in Washington, the new tariffs were substantially larger than industry watchers had expected, Reuters said.

China’s Ministry of Commerce quickly accused the U.S. of protectionism and said the imposition of tariffs endangered Sino-U.S. cooperation in the search for renewable energy sources.

Still, China did not signal any specific response to the tariffs.

Shares of solar panel makers did not seem to benefit from the news. Trina Solar (NYSE:TSL) fell more than 5% in Friday trading, while First Solar (NASDAQ:FSLR) shares fell more than 7%, and SunPower (NASDSAQ:SPWR) saw its shares plunge more than 10%

The solar panel tariffs come on top of other tariffs imposed against pencils, steel pipes, electric blankets and bed-spring manufactured in China. With the U.S. presidential race looming, American politicians have promised to defend against unfair Chinese trade practices.

American solar company executives were pleased with the government’s decision.

Analysts cited by Reuters said that the tariffs would only give American solar panel makers breathing room in the U.S. Chinese solar panels would continue to be sold abroad, setting the prices in those markets. Chinese manufacturers currently account for 60% of the worldwide solar panel market.