WASHINGTON — U.S. President Donald Trump on Thursday signed a proclamation to impose a 15 percent tariff on polysilicon derivative products, a move intended to protect America's polysilicon manufacturing, which is crucial for semiconductor and solar panel production. The latest trade action will take effect at 12:01 a.m. on Dec. 4 (Washington time), the White House said, as South Korea's chip industry has been closely monitoring the U.S. measure for its potential impact on business operations in the United States. The proclamation also includes the imposition of minimum import prices for polysilicon and its derivatives, as the U.S. is stepping up efforts to maintain its technological edge amid intensifying competition with China over artificial intelligence (AI) and other cutting-edge technologies. "Polysilicon is the base material underpinning the security of America's semiconductor and solar-power supply chains. Yet for decades, America has allowed foreign countries to weaken U.S. producers in the polysilicon sector, eroding our economic and national security," Trump said in the pro