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.

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

Cambodia, Vietnam, Thailand and Malaysia's solar panel makers will face record-high US solar tariffs announced on Monday.