U.S. automakers worry that President Donald Trump's agreement to tariff Japanese vehicles at 15% would put them at a competitive disadvantage, saying they will face steeper import taxes on steel, aluminum and parts than their competitors.

"The trade deal struck with the U.S. is certainly a relief in that it offers some certainty that U.S. tariffs on Japan-made cars won't rise to punitive levels," said Stefan Angrick, head of Japan and Frontier market economics at Moody's Analytics.

The preliminary agreement suggests there is a path forward to lowering the auto duties on other major trading partners, as well.