"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.

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