US President Donald Trump has signed a proclamation imposing a 15% tariff on polysilicon and its derivative products, targeting a material that underpins both semiconductor and solar panel manufacturing. The measure, signed on 6 August and set to take effect on 4 December, also establishes minimum import prices — $21 per kilogram for polysilicon, $100 per kilogram for ingots and wafers, $0.22 per watt for solar cells, and $0.38 per watt for solar modules. The White House said the action was taken under Section 232 of the Trade Expansion Act of 1962, a law that grants the president authority to restrict imports deemed a threat to national security.

Polysilicon is the foundational raw material from which silicon wafers are cut for use in AI chips and other advanced semiconductors. Trump noted in the proclamation that the United States once produced roughly half of the world's polysilicon supply; by 2024 that figure had collapsed to less than 2%, while China now holds a near monopoly on global production. Commerce Secretary Howard Lutnick framed the tariff as a tool to prevent Chinese producers from undercutting American manufacturers through below-cost pricing, known as dumping. "We're making the products here, but we need the supply chain here," Lutnick said, adding that the minimum price regime would stop Chinese producers from flooding the market. The measures are expected to benefit Hemlock Semiconductor and Wacker Chemie, the two main US-based producers of the material. Washington has also said it will offer incentives to encourage domestic production.

China's embassy in Washington pushed back sharply, saying the move "seriously disrupts" bilateral trade and that Beijing would take steps to protect its companies. The embassy accused the US of "abusing state power" and argued that protectionism would not make American industry more competitive. Chinese state media cited analysts who described the tariff as the latest in a series of US moves to limit China's role in critical technology supply chains — a list that already includes restrictions on drone and humanoid robot imports.

The announcement lands against a backdrop of sustained US-China economic rivalry centred on artificial intelligence and advanced chips. A broader tit-for-tat tariffs dispute between the two countries has been on hold since May 2025, but tensions have continued to simmer. This week Beijing announced its own countermeasures, including tighter export controls on drones and a national security review of imported printers and copiers. South Korea's semiconductor industry, which is deeply integrated into global chip supply chains, has also been closely monitoring the US measure for its potential knock-on effects. The December start date gives companies roughly four months to adjust before the new rules take hold.