One day after the Wisconsin-based company said it was planning to shift some manufacturing overseas due to the European Union's tariffs in retaliation for US duties, Trump accused Harley-Davidson of appropriating the trade war as an "excuse" for the move.
EU officials, meanwhile, suggested Trump had only himself to blame for the falling-out with a company he had previously hailed as "a true American icon."
The EU responded to US tariffs on steel and aluminum by hitting a series of American products with import taxes, including motorcycles, bourbon and blue jeans.
"We don't want to punish but that is the unfortunate consequence, that (US companies) will put pressure on the American administration to say hey, hold on a minute, this is not good for the American economy," EU Trade Commissioner Cecilia Malmstrom said at a news briefing.
In a series of caustic early-morning tweets, Trump dismissed any notion that his policies were responsible for Harley-Davidson's move.
"Early this year Harley-Davidson said they would move much of their plant operations in Kansas City to Thailand. That was long before Tariffs were announced. Hence, they were just using Tariffs/Trade War as an excuse," he said.
"Harley must know that they won't be able to sell back into US without paying a big tax!"
Trump, speaking later at the White House, defended his criticism of Harley-Davidson and said his hard line on trade would yield results.
"Bottom line is that companies are coming back now to negotiate, including (the) European Union that wants to negotiate," Trump said. "Because if they don't, we're going to tax their cars."
Harley-Davidson did not respond to request for comment but has said the move overseas was to avoid EU tariffs, not to sell in the US market.
The company has repeatedly described the Thailand factory, along with other overseas production, as vital to its long-term need to boost foreign markets to make up for sluggish sales in the United States.