President Donald Trump sharply escalated his criticism of Canada on Sunday, accusing the country of "ripping" the United States off "for decades" as he defended his tariff policies and called on Canadian companies to relocate their operations south of the border.

In back-to-back posts on Truth Social on Sunday afternoon, Trump first credited tariffs with strengthening the U.S. auto industry and keeping American manufacturing plants open.

"When I announced that I was running in the 2024 Presidential Election, right at the beginning, Ford was getting ready to close their Big Factory, in Detroit," Trump wrote.

He claimed the plant is now "running 24/7" and has become "one of the most profitable Car Plants in the World."

"There are many other examples, for both Ford, General Motors, and others. I've revived, and indeed saved, the Automobile Business in our America. That's because of what I've done with TARIFFS," he said.

Trump then turned his focus to Canada, describing the longtime U.S. ally as one of the country's "worst" trade offenders.

"One of the Worst Abusers is Canada. I don't want Canadian cars, I don't want Canadian parts, I don't want Canadian anything. They've been ripping us off for decades, and it's going to stop," Trump wrote.

"This should have happened long ago with other Presidents, just as stopping Iran should have happened long ago," he continued. "They want to be treated like a State, but they aren't one. I deal with the Leadership of many Countries, but I find Canada to be the worst. They are entitled no longer!"

Minutes later, Trump followed up with a second post urging Canadian companies that do business with the United States to move their operations there immediately.

"Let all Canadian Companies that are doing business with America move to the United States, immediately. Many of them are Companies that moved out years ago due to stupid U.S. Leadership. When you move back, there are no TARIFFS!" Trump wrote.

The president's remarks come amid escalating trade tensions between the two countries. U.S. tariffs of 50% on approximately $20 billion worth of Canadian goods took effect on Aug. 22 after trade talks collapsed, according to Reuters. Canada retaliated with tariffs on roughly $20 billion in U.S. imports that are set to take effect Sept. 8.

The stakes are significant for both economies. Canada and the United States are each other's largest trading partners, with cross-border trade in goods and services totaling hundreds of billions of dollars annually under the framework of the U.S.-Mexico-Canada Agreement (USMCA), the trade pact that replaced NAFTA in 2020. The automotive sector in particular is deeply integrated across the border, with vehicles and parts often crossing multiple times during production, which is why tariffs on Canadian autos and parts have drawn sharp attention from automakers on both sides. Canadian Prime Minister Mark Carney, who took office earlier this year, has said Canada's response to U.S. trade actions is aimed at pressuring the U.S. to return to negotiations.

The White House, the office of Canadian Prime Minister Mark Carney, Ford Motor Co., and General Motors did not immediately respond to requests from FOX Business for comment.

Reuters contributed to this report.