Donald Trump has vowed to reciprocate against "unfair" European Union trade duties on Harley Davidson motorbikes.
The US President had previously criticised the US bike maker for its plans to shift American production overseas to avoid EU tariffs.
But on Tuesday, after Harley blamed the 31% duties for a large drop in profits, Mr Trump appeared to back the firm.
Responding to comments on Fox Business on Twitter, he said the duties were "so unfair", adding: "We will Reciprocate!"
The broadside comes ahead of talks aimed at calming trade tensions between the EU and the US.
Last June, the EU imposed tariffs on a raft of US-made goods in retaliation for duties the White House had placed on imported steel and aluminium.
It meant tariffs on Harleys climbed from 6% to 31%, and they are set to rise further in 2021.
On Tuesday, the US firm said that various trade spats between the US and its partners would cost it between $100m (£77m) and $120m in 2019.
This was partly because of Chinese tariffs, which have increased to 55% as a result of the trade war between the world's two biggest economies.
But the firm said "the big impact" would be from the EU duties, adding they had also contributed to a 27% fall in profits to $127.9m in the first quarter.
Analysts say the company's trade worries compound years of fading interest in the brand, whose heyday was in 1960s and 70s.
President Trump and the head of the European Commission, Jean-Claude Juncker, agreed last year that they wanted to reduce trade barriers.
And earlier in April the EU approved plans for formal trade talks with the US.
But earlier this year news reports suggested that the US was considering new tariffs on EU imported vehicles.
Mr Juncker later said Mr Trump had assured him there were no plans to do this "for the time being", but vowed an immediate response if the tariffs went ahead.