The Trump administration has imposed tariffs on steel and aluminium from Europe, Mexico and Canada, prompting stock prices to plummet and ramping up fears of a trade war.
After the announcement, stocks for industrial companies fell as they faced the prospect of paying more for metals they use to make aircraft and machinery.
Companies that make household items took some of the worst losses, as products including orange juice and peanut butter might be hit with European tariffs, introduced in retaliation to the move by Trump.
The EU has already threatened to counterpunch by targeting US products, including Kentucky bourbon, blue jeans and motorcycles.
The US tariff – 25% to be imposed on imported steel and 10% on aluminium –will come into effect from Friday.
President Trump had originally imposed the tariffs in March, saying reliance on imported metals threatened national security. But he exempted Canada, Mexico and the European Union to buy time for negotiations – a delay that expired at midnight on Thursday.