German auto manufacturers are nervously waiting to see if President Donald Trump will act on a secret Commerce Department report on how imported car parts might affect national security.

Trump has complained about the German cars' presence on U.S. streets and tweeted threats to tax European, and particularly German, automakers' vehicles.

It is thought the "232" report, as it is informally referred to, could recommend tariffs as high as 25 percent on auto parts and cars imported into America.

Speaking Wednesday, the U.S. leader said he was prepared to introduce auto tariffs if a wider trade deal with the EU cannot be renegotiated.

"We're trying to make a deal, they're very tough to deal with," said Trump before adding "if we don't make a deal, we'll do the tariffs."

Auto analysts Evercore ISI has stated that based on a 25 percent import tariffs, Germany's big three auto firms would see an immediate 6.25 billion euro ($7 bn) hit to earnings before interest and tax each year.

Under their model, Volkswagen Group would lose around 2.5 billion euros while Mercedes-maker Daimler would suffer a 2-billion-euro loss and BMW would see earnings fall by 1.7 billion euros.