If the findings show a threat to the USA, a 1960s-era trade law gives Trump authority to impose import restrictions without congressional approval.
The new European Union tariffs enacted Friday apply to billions of dollars' worth of American goods - including jeans, bourbon and motorcycles.
Trump has proposed imposing duties on $400 billion more if China doesn't further open its markets to US companies and reduce its trade surplus with the United States.
The threat came the same day the European Union imposed new tariffs on American products, a retaliatory move for the tariffs Trump applied on steel and aluminum.
Earlier in the week, news reports emerged that Daimler, which produces Mercedes-Benz autos, and other German automakers were pitching a reciprocal elimination of tariffs. Industry data shows that German automakers build more vehicles in southern U.S. states that voted for Trump in the 2016 presidential election than they ship to the United States from Germany.
EU Trade Commissioner Cecilia Malmstrom said this week that the 28-nation bloc was "left with no other choice" but to impose tariffs of its own after the "unilateral and unjustified decision of the United States". That investigation is ongoing, but Ross told a conference on Thursday he expects the national security investigation into automobiles to conclude by late July or August. It exported more than 70% of those cars to other countries.
Trump has repeatedly warned he would not hesitate to slap additional duties on foreign imports to protect the U.S. auto industry - notably on German cars.
Trump has threatened duties on up to $450 billion of imports from China.
He said: "We don't want to fight in public via Twitter".
American farmers still bear the brunt of Beijing's planned tariffs. That said, if the current tough talk on trade translates into thorough tariffs, the USA dollar could ultimately benefit as traders seek out the perceived safety of the world's reserve currency, even if USA economic growth takes a hit. Nevertheless, the Tweet spooked European automakers, particularly those in Germany.
Iran rebuffs Trump's call for OPEC to increase oil output | AP business
The US West Texas Intermediate (WTI) crude priced US$66.49 per barrel, up 1.5 per cent from the last close, said the source . Al Mazrouei said that OPEC and its allies would now work to boost production by up to 1 million barrels a day.
The U.S. imported about 1.26 million vehicles annually from Europe in 2017, according to LMC Automotive. "Automakers support reducing trade barriers across the board".
US President Ronald Reagan hits pasta imports from Europe in order to protect the domestic industry.
Earlier this month, Mexico imposed a series of tariffs on $3 billion worth of United States exports of pork, apples, potatoes, bourbon as well as different types of cheese.
German-built vehicles exported to the United States fell 10 percent to 494,000 vehicles, while German automakers produced 804,000 vehicles in the United States a year ago.
It is hard for the White House to unilaterally impose tariffs without input from Congress, but Trump has found several ways to do it this year.
The tariff proposal has drawn sharp condemnation from Republican lawmakers and business groups.
The Auto Alliance has said it was "confident that vehicle imports do not pose a national security risk". The commission, the bloc's executive arm, said that the 1 trillion euros in commerce between the EU and U.S.is equitable, and it disputed Trump's assertion that the EU needs to be punished because of unfair trade practices, according to an internal EU memo obtained by Bloomberg.
Of their US sales, BMW imported 70.8 percent from Europe, Mercedes maker Daimler 51.9 percent and Volkswagen 45 percent, according to LMC.