On Saturday, Trump finally signed off on threatened 25-percent tariffs on neighboring Mexico and Canada -- despite sharing a free trade pact -- and hit China with a 10-percent tariff in addition to already enacted levies.

The move provoked immediate vows of retaliation, while analysts warned the ensuing trade war would likely decrease US growth and raise consumer prices over the short term.

"Will there be some pain? Yes, maybe (and maybe not!)" Trump wrote Sunday morning in all-caps on his Truth Social media platform.

"But we will Make America Great Again, and it will all be worth the price that must be paid," he added.

On Friday, the right-leaning editorial board of the Wall Street Journal newspaper blasted Trump's proposed tariffs in a piece titled "The Dumbest Trade War in History."

Trump clapped back on Sunday, saying: "The 'Tariff Lobby,' headed by the Globalist, and always wrong, Wall Street Journal, is working hard to justify... the decades long RIPOFF OF AMERICA, both with regard to TRADE, CRIME, AND POISONOUS DRUGS."

He has long decried US trade deficits as a sign of other countries taking advantage of Americans.

"THOSE DAYS ARE OVER!" he said.

In a separate post, Trump called again for Canada to become a US state, heightening tensions further with one of his country's closest allies after hitting it with heavy tariffs.

While claiming the United States pays "hundreds of billions of dollars to SUBSIDIZE Canada," Trump said "without this massive subsidy, Canada ceases to exist as a viable Country."

"Therefore, Canada should become our Cherished 51st State," he wrote on Truth Social, claiming the move would bring "much lower taxes, and far better military protection for the people of Canada - AND NO TARIFFS!"

The US Census Bureau listed the 2024 trade deficit in goods with Canada as $55 billion.