Solar cells from four Southeast Asian countries that have been major suppliers to the US are facing newly increased tariffs, hiked up as high as 3,521 percent.

The tariffs affect Cambodia, Malaysia, Thailand, and Vietnam, which together accounted for more than three quarters of total module imports last year, according to Bloomberg. The tariffs essentially make the products “unmarketable” in the US, the Wall Street Journal reports.

The move comes after long-running Commerce Department investigations into whether Chinese companies were funneling products through Southeast Asia to avoid tariffs and lower prices. It also heightens Donald Trump’s trade war with China after roiling global markets with drastic tariff proposals this month. The president called a 90-day pause on tariffs, excluding China.

US solar companies have been split on what to do about cheap solar cells from Southeast Asia. Domestic manufacturers petitioned the Commerce Department to investigate, while renewable energy project developers are worried about the tariffs raising costs for construction and the manufacturing of panels in the US using imported cells.

Cambodia refused to comply with the investigation, and got hit with the highest tariffs at 3,521 percent. Duties for companies in Vietnam reach as high as 395.9 percent, 375.2 in Thailand, and 34.4 for Malaysia.

The US International Trade Commission still has to weigh in on the proposed tariffs in June to finalize them.