The U.S. has slapped Chinese solar companies with high-import tariffs for dumping solar panels in the U.S. market at unduly low prices.

The U.S. Commerce Department sided with U.S. solar companies on Thursday and agreed to impose preliminary anti-dumping tariffs on Chinese firms undercutting domestic companies' prices. The department announced the Chinese companies including Suntech Power Holdings Co., Ltd. and Trina Solar Ltd. will have to pay anti-dumping tariffs ranging from 30 percent or more. It noted that some firms may even face tariffs up to 250 percent.

The Commerce Department said a final ruling will be announced in early October.

The recent preliminary ruling comes after the Commerce Department decided to impose two-point-nine to four-point-73 percent countervailing duties on Chinese-made solar panels in March, which is expected to further stress trade tensions between the two countries.