US trade officials finalized steep tariff levels on most solar cells from Southeast Asia, a key step toward wrapping up a year-old trade case in which American manufacturers accused Chinese companies of flooding the market with unfairly cheap goods.

The US Commerce Department has announced plans to impose tariffs of up to 3,521% on imports of solar panels from four South East Asian countries. It comes after an investigation that began a year ago when several major solar equipment producers asked then-President Joe Biden administration to protect their US operations.

U.S.-based manufacturers say that Chinese companies based in Cambodia, Vietnam, Thailand, and Malaysia are dumping cheap solar panels on the American market.