President Donald Trump announced an increase in tariffs on Canadian steel and aluminum imports by an additional 25%, bringing the total to 50%, in response to Ontario's 25% tax on electricity exports to the U.S.

Ontario Premier Doug Ford stated he would maintain the 25% tax on U.S. energy and threatened to shut off the province's energy supply to the U.S. if necessary.

The Dow Jones Industrial Average fell more than 500 points following Trump's announcement, with the S&P 500 dropping 0.8% and the Nasdaq Composite falling 0.4%.

Trump has not yet signed the formal paperwork to raise tariffs on Canada's steel and aluminum, but the order is reportedly in progress.

Trump also demanded that Canada drop tariffs on U.S. dairy products and warned of a potential national emergency declaration on electricity if the situation escalates.