U.S. President Donald Trump issued a stern ultimatum to the European Union on Wednesday, warning that if a comprehensive trade pact is not brokered, Washington will tax European car imports.

"We’re trying to make a deal. They’re very tough to make a deal with -- the EU," Trump said while hosting his Austrian counterpart, Sebastian Kurz, at the White House.

"If we don’t make the deal, we’ll do the tariffs," he said.

The comments follow Trump's receipt over the weekend of a study compiled by the Commerce Department that is widely expected to open the door for Trump to impose tariffs of up to 25 percent on European auto imports over alleged national security concerns.

Referring to the report, Trump said the administration has studied possible tariffs "very carefully".

"We’ve seen the results. But the bottom-line result is whether or not we can make a deal with the EU that’s fair," he said. "So we’ll see what happens."

Trump in August threatened to hit European cars with a 25 percent tariff during a trade spat that has largely cooled amid ongoing negotiations agreed to by Trump and European Union Commissioner Jean-Claude Juncker to reduce trade barriers.