Some of the world’s largest solar equipment makers on Wednesday asked President Joe Biden’s administration to impose tariffs on panels and cells from four Asian countries to protect billions of dollars in investments in U.S. manufacturing.

First Solar and six other manufacturers allege that Cambodia, Malaysia, Thailand and Vietnam are flooding the U.S. market with cheap solar cells that threaten the domestic industry.

Blaming illegal subsidies in China for artificially lowering the price of panels, Qcells and at least six other U.S. solar manufacturers filed a petition Wednesday urging the federal government to crack down.

Firms warn that China uses its neighbors to skirt existing levies, depressing prices and threatening U.S. investments.

“We are seeking to enforce the rules, remedy the injury to our domestic solar industry, and signal that the U.S. will not be a dumping ground for foreign solar products.”

Treasury Secretary Janet Yellen arrived in China on Thursday for five days of meetings in a nation determined to avoid open conflict with the United States, yet the world’s two largest economies still appear to be hashing out the rules on how to compete against each other.

Beijing is set to further increase its manufacturing and installation of solar panels as it seeks to master global markets and wean itself from imports.

Chinese solar giant Longi Green Energy Technology Co. is calling on Beijing to crack down on low prices and ensure panel quality as excess capacity and fierce competition spur company failures.