Producers of steel and aluminum around Asia are getting hammered by U.S. President Donald Trump’s plan to hike tariffs on imports and the risk of a global tit-for-tat trade war.

Steel mills led losses with South Korea’s Posco, Japan’s Nippon Steel & Sumitomo Metal Corp. and the listed unit of China’s biggest producer, Baoshan Iron & Steel Co., all tumbling more than 3.5 percent. Aluminum smelters also slid with UACJ Corp. down 2.8 percent in Tokyo and China Hongqiao Group, the country’s biggest producer, sliding 2.6 percent.

Trump said the U.S. will impose tariffs of 25 percent on imported steel and 10 percent on aluminum for “a long period of time,” and he expects to sign a formal order next week. While he has made no secret of his intention to protect American interests against foreign markets, the threat that other nations will retaliate is prompting concern that key export markets will be shut off to producers around the world.

“You have to say Asian steel producers generally will be the worst hit given that they are the biggest producers,” Gavin Wendt, senior resource analyst at MineLife Pty in Sydney, said by phone. “There would naturally be more of an impact on them in terms of volume.”

Much of Trump’s protectionist agenda is directed at China, although the Asian nation isn’t a major exporter of steel to the U.S. That didn’t stop shares in its biggest mills dropping as news of the tariffs broke. In addition to Baoshan, notable decliners included Hesteel Co. and Angang Steel Co.

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China accounts for just 2 percent of U.S. imports, and its shipments generally are falling as robust domestic growth soaks up metal and the government cuts capacity as part of a drive to clean up the environment. Still, the prospect of tit-for-tat retaliation by producers around the world was enough to spook investors.

The planned tariffs raise “risks of an all-out trade war, which could dampen economic growth and weigh on the sector,” Australia & New Zealand Banking Group Ltd. said in note.

The impact is potentially much greater for China’s aluminum industry, the fourth-biggest supplier to the U.S. Aluminum Corp. of China Ltd. losing 1.5 percent in Hong Kong. The U.S. took 14 percent of China’s aluminum exports last year, as the Asian nation’s overseas shipments and production both rose to a record.

It’s not all bad news in Asia. Australia’s BlueScope Steel Ltd., which operates a mill in the U.S., rose 0.3 percent Friday. The company’s Chief Executive Officer Mark Vassella said in a Bloomberg TV on Feb. 26 that it expects a positive impact on earnings at its North Star plant in Delta, Ohio to outweigh any losses on U.S. exports.

Japan’s Yamato Kogyo Co. climbed 3.5 percent after SMBC Nikko said in a report that the company has a “large H-beam operation” in the U.S.