Washington DC - President Donald Trump said Tuesday he would "probably" reconsider doubling planned tariffs on Canadian steel and aluminum, hours after announcing the sharp hike.

Trump's step up to 50% levies initially came after the Canadian province of Ontario imposed an electricity surcharge on three US states that buy it – but Ontario has suspended this decision after talks with Washington.

Asked if the change would influence his decision on Canada tariffs, Trump told reporters: "I'm looking at that, but probably so."

Trump's threats came shortly before a midnight deadline for ramping up a globe-spanning trade offensive with 25% levies on steel and aluminum imports.

Donald Trump US Secret Service shoots armed man near White House

The US dollar fell sharply on Tuesday, particularly against the euro, while markets fluctuated in volatile trading.

Canadian Prime Minister-elect Mark Carney earlier vowed that his incoming administration would hit back with "maximum impact."

But Ontario has since agreed to halt the 25% fee on electricity exports to Michigan, Minnesota, and New York after Premier Doug Ford said he held "productive" talks with US Commerce Secretary Howard Lutnick.

Ford, Lutnick, and US Trade Representative Jamieson Greer will meet in Washington on Thursday "to discuss a renewed USMCA ahead of the April 2 reciprocal tariff deadline," said a US-Canada joint statement, referring to the North American trade pact.

The upcoming steel and aluminum levies, which currently contain no exceptions, threaten to affect everything from electronics to vehicles and construction equipment – and have manufacturers scrambling to find cost-effective domestic suppliers.

Trump said his supercharged tariffs were in response to Ontario's electricity surcharge.

He added on Truth Social that if Canada uses electricity as a bargaining chip "they will pay a financial price for this so big that it will be read about in History Books for many years to come!"

He also threatened to boost tariffs on cars from April 2, saying this would "essentially, permanently shut down the automobile manufacturing business in Canada."

Lauren Boebert Lauren Boebert facing censure over shocking "pimp cane" comment about Al Green

Trump has vowed reciprocal levies as soon as April 2 to remedy trade practices Washington deems unfair, raising the potential for more products and trading partners to be specifically targeted.

Reacting to Trump's announcement on MSNBC, Ontario Premier Doug Ford said the US president made "an unprovoked attack on our country, on families, on jobs."

Trump, meanwhile, backed up his tariff threats by saying again that Canada should be absorbed.

The "only thing that makes sense" is for Canada to join the US as a 51st state, he said. "This would make all Tariffs, and everything else, totally disappear."