The case was brought last year by the Korean company Hanwha Qcells, Arizona-based First Solar and several smaller solar panel makers in the US. They accused Chinese companies with factories in Malaysia, Cambodia, Thailand and Vietnam of shipping panels priced below their cost of production, owing to unfair state subsidies.

However, critics, including the Solar Energy Industries Association trade group, have said tariffs would harm US solar producers because they would raise prices on the imported cells that are assembled into panels at American factories.