The European Union last week raised tariffs on Harley-Davidson motorcycles to 31 percent from 6 percent. The company said the increase would add $2,200 on average to the cost of a motorcycle exported to Europe from the United States. Harley-Davidson said it would not raise the suggested prices of its motorcycles to cover the cost of the tariffs. It expects, at least for a little while, to bear the additional expense of the tariffs itself, which would cost the company an estimated $90 million to $100 million a year. Over the longer term, Harley-Davidson, based in Milwaukee, intends to make more motorcycles in countries that are not subject to the tariffs. That plan could take nine to 18 months to put into effect, the company said.

A year ago, Mr. Trump lauded the firm for manufacturing in the United States. “We’re proud of you! Made in America, Harley-Davidson,” he said, when executives from the company drove motorcycles onto the White House lawn.

Harley-Davidson’s announcement may make it more likely that Mr. Trump imposes tariffs on European cars, to further pressure the European Union to make trade concessions. But such actions may invite more retaliation from the bloc, and, in turn, more of the sorts of announcements that Harley-Davidson made. The administration may hope that the strong United States economy will allow American companies to better weather the trade battles — and that other countries will ultimately cave because they cannot afford to lose access to the United States market.

Still, negative corporate announcements bring a jarring specificity to trade wars that can spread through financial markets and the wider economy. Harley-Davidson’s stock was down over 7 percent on Monday. The Standard & Poor’s 500-stock index was down 1.8 percent. The benchmark is now only up 1.1 percent since the end of 2017 and down 5.9 percent from its all-time high. The trade war appears to have halted the Trump rally. And there are a lot more Harley-Davidsons on the stock market.