The European Union has warned that the nearly 300 billion of U.S. exports could be hit with retaliatory tariffs if the Trump administration decides to slap duties on imported European cars.
The figure amounts to 19 percent of total American exports last year.
In a paper to the US Commerce Department, sent last Friday, the EU said the department's investigation of European cars and auto parts, on the grounds of national security, was unjustifiable.
It added that any tariffs imposed as a result of the probe would also cost the U.S. more than four million American jobs.
Trump has repeatedly criticized the EU over its trade surplus with the U.S. and for having higher import duties on cars.
The EU has a 10 percent levy on American-built cars.
The U.S. taxes 2.5 percent on European-built cars, but 25 percent on European vans and pick-up trucks