US President Donald Trump said late on Thursday that he was ending "all trade negotiations" with Canada because of a television ad opposing US tariffs that he said misstated the facts and called "egregious behaviour" aimed at influencing US court decisions.

The post on Trump's social media site came after Canadian Prime Minister Mark Carney said he aims to double his country's exports to countries outside the US because of the threat posed by Trump's tariffs.

Trump's call for an abrupt end to negotiations could further inflame trade tensions that have already been building between the two neighbouring countries for months.

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Trump posted, "The Ronald Reagan Foundation has just announced that Canada has fraudulently used an advertisement, which is FAKE, featuring Ronald Reagan speaking negatively about Tariffs."

"The ad was for $75,000. They only did this to interfere with the decision of the US Supreme Court, and other courts," Trump wrote on his social media site.

"TARIFFS ARE VERY IMPORTANT TO THE NATIONAL SECURITY, AND ECONOMY, OF THE USA Based on their egregious behaviour, ALL TRADE NEGOTIATIONS WITH CANADA ARE HEREBY TERMINATED."

Carney's office didn't immediately respond to a request for comment. The prime minister was set to leave Friday morning for a summit in Asia, while Trump is set to do the same Friday evening.

Earlier on Thursday night, the Ronald Reagan Presidential Foundation and Institute posted on X that an ad created by the government of Ontario "misrepresents the 'Presidential Radio Address to the Nation on Free and Fair Trade' dated April 25, 1987."

It added that Ontario did not receive foundation permission "to use and edit the remarks."

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The foundation said it is "reviewing legal options in this matter" and invited the public to watch the unedited video of Reagan's address.

Carney met with Trump earlier this month to try to ease trade tensions, as the two countries and Mexico prepare for a review of the US-Mexico-Canada Agreement — a trade deal Trump negotiated in his first term, but has since soured on.

More than three-quarters of Canadian exports go to the US, and nearly $CA3.6 billion ($3.95 billion) worth of goods and services cross the border daily.

Trump said earlier this week that he had seen the ad on television and said that it showed that his tariffs were having an impact.

"I saw an ad last night from Canada. If I was Canada, I'd take that same ad also," he said then.

In his own post on X last week, Doug Ford, the premier of Ontario, posted a link to the ad and the message: "It's official: Ontario's new advertising campaign in the US has launched."

He continued, "Using every tool we have, we'll never stop making the case against American tariffs on Canada. The way to prosperity is by working together."

A spokesperson for Ford didn't immediately respond to a request for comment Thursday night. But Ford previously got Trump's attention with an electricity surcharge to US states.

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Trump responded by doubling steel and aluminium tariffs.

The president has moved to impose steep US tariffs on many goods from Canada.

In April, Canada's government imposed retaliatory levies on certain US goods, but it carved out exemptions for some automakers to bring specific numbers of vehicles into the country, known as remission quotas.

Trump's tariffs have especially hurt Canada's auto sector, much of which is based in Ontario. This month, Stellantis said it would move a production line from Ontario to Illinois.

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The University of Adelaide is under investigation after admitting to underpaying more than 830 former casual academic staff $1.25 million over eight years.

The institution confirmed it uncovered underpayments to staff between March 2017 to May 2025 after ramping up its auditing and payment monitoring due to the prevalence of underpayments within the industry.

The audit found that hundreds of current and former casual academic staff with a PhD or in a course coordinator role were not paid the higher rates they were entitled to.

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This led to 838 staff being underpaid about $1.25 million. 

"While this represents less than 0.05 per cent of salary payments over that period, it is still unfortunate and very regrettable," a University of Adelaide spokesperson said.

"The university deeply regrets that the underpayments occurred and is remediating staff as quickly as possible.

"Impacted current and former staff have been contacted and repayments have started."

The university has notified the Fair Work Ombudsman.

"We will continue to implement, enhance, and strengthen our processes and controls," the spokesperson said.

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"The university's auditing and monitoring activities are continuing, and if any other instances of underpayments are identified, affected staff will be contacted by the university and remediated as quickly as possible."

The Fair Work Ombudsman said it is investigating the underpayments.

"We expect any employers that identify non-compliance to fully cooperate with our investigations," a spokesperson said in a statement.

"It is not appropriate to comment further."

Any staff from the university who may have concerns should contact the ombudsman.

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Fair Work began targeting systemic non-compliance in the university sector in 2022, which the National Tertiary Education Union has labelled as a "wage theft epidemic".

The ombudsman has entered into enforceable undertakings with the University of Sydney, University of Technology Sydney, University of Newcastle, La Trobe University, University of Melbourne, Charles Sturt University and Griffith University.

It has won court penalties against the University of Melbourne and has ongoing legal action against the University of NSW. 

The University of Wollongong has recently repaid $6.6 million to more than 5000 underpaid staff.

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