US President Donald Trump is unlikely to act immediately to slap tariffs on automotive imports even if his administration dubs them a threat to national security — and could wait weeks or months before taking action, according to lobbyists and analysts following the issue in Washington.

By Sunday night, the US commerce department is expected to transmit a long-awaited report to Mr Trump about its investigation of the national security risk posed by imported cars and car parts, a subject that has threatened to inflame trade tensions — most acutely with the EU and Japan, but also South Korea.

The report does not have to be publicly released, so its contents may not be immediately known. But car industry executives fear that it will include a recommendation for sweeping tariffs on imported vehicles and parts that could inflict serious damage on their businesses.