Big tech stocks fell on Tuesday. SMCI down 7%; Oracle, Tesla, Nvidia, Broadcom fell around 3%; Amazon, Meta, Alphabet down over 2%.
Trump said he would impose additional 10% levies from February 1 on goods imported from Denmark, Norway, Sweden, France, Germany, the Netherlands, Finland and Britain, rising to 25% on June 1 if no deal on Greenland was reached.
Major European Union states condemned the tariff threats as blackmail, and France proposed responding with a range of previously untested economic countermeasures. The EU and Britain had agreed trade deals with the U.S. last year.
"There is obviously a response (in financial markets) to the new tariff threats," said George Lagarias, chief economist at Forvis Mazars.
"It's highly likely that the White House will use the threat of tariffs consistently, even when deals have previously been agreed."
The EU's retaliation options include a package of its own tariffs on 93 billion euros ($108 billion) of goods imported from the U.S. that was suspended for six months in early August, and measures under an Anti-Coercion Instrument that could hit U.S. services trade or investments.
The tariff threats should also make for a fraught few days at Davos as leaders from around the world gather in Switzerland at the World Economic Forum, including a large U.S. group led by Trump.