European shares fell on Monday, led by automobiles, as the U.S. President Donald Trump's latest threat to impose steep tariffs on the European Union and Mexico kept investors on edge.

Economists had already downgraded growth for the European Union, and the new duties would hit industries there especially hard. Companies are looking for ways to blunt the impact.

Many economists already believe it’s a matter of time before Americans start to see sticker shock from the tariffs President Donald Trump has enacted. That timeline could speed up even more if Trump follows through with his latest package of tariff threats slated to take effect in three weeks.