U.S. futures and global stocks were hit by a selloff early on Monday as markets around the world braced for a potential trade war triggered by President Donald Trump’s decision to impose sweeping tariffs on imports from Canada, Mexico, and China—which warned of “necessary countermeasures.”

The new tariffs on imports from all three nations ‒ which are on top of existing taxes and go into effect on Tuesday.

The stock market fell on Monday after President Donald Trump slapped tariffs on Canada, Mexico and China, eliciting threats of retaliation and setting the stage for a trade war. The Dow Jones Industrial Average slid about 550 points, or 1.25%, in early trading on Monday. The S &P 500 dropped 1.5%, and the tech-heavy Nasdaq plummeted 2%.

Shares in Europe and Asia have fallen after US President Donald Trump announced tariffs on Canada, Mexico and China, and said tariffs on the EU would "definitely happen". The German and French stock markets were down about 2%, with shares in carmakers among the worst hit, while London's FTSE 100 dropped more 1%.

Wall Street's main indexes dropped at the open on Monday as fears of a full-blown trade war and its impact on the global economy jolted markets around the world after President Donald Trump levied steep tariffs on Mexico,