Donald Trump has threatened to stop the opening of the massive Ontario–Michigan bridge linking Windsor and Detroit and hit out at former President Barack Obama for granting Canada a waiver that allowed the project to bypass Buy American protections.

In a blistering post to his Truth Social on Monday evening, Trump accused Canada of exploiting the US and vowed he would block the Gordie Howe International Bridge project from moving forward unless America is compensated and treated with what he called 'fairness and respect.'

'President Barack Hussein Obama stupidly gave them a waiver so they could get around the BUY AMERICAN Act, and not use any American products, including our Steel,' Trump wrote.

Trump claimed Canada had benefited unfairly from American concessions.

'I will not allow this bridge to open until the United States is fully compensated for everything we have given them, and also, importantly, Canada treats the United States with the Fairness and Respect that we deserve,' Trump wrote.

The president's extraordinary threat targets one of the most consequential infrastructure projects on the northern border. 

The towering cable-stayed span across the Detroit River is expected to transform trade and transportation between the two countries.

Trump's post unleashed a sweeping indictment of the project and Canada's role in it, arguing that the United States had been sidelined in the construction of a bridge connecting its own territory.

'As everyone knows, the Country of Canada has treated the United States very unfairly for decades,' Trump wrote.

'But imagine, Canada is building a massive bridge between Ontario and Michigan. They own both the Canada and the United States side and, of course, built it with virtually no US content.'

He singled out Obama, accusing his predecessor of undermining American industry.

'President Barack Hussein Obama stupidly gave them a waiver so they could get around the BUY AMERICAN Act, and not use any American products, including our Steel,' Trump wrote.

Trump went even further, suggesting the United States should hold an ownership stake in the project.

'With all that we have given them, we should own, perhaps, at least one half of this asset,' he said, adding: 'The revenues generated because of the US Market will be astronomical.'

Trump's anger centers on a waiver negotiated during Obama's presidency that allowed the bridge to bypass strict 'Buy American' requirements.

The waiver permitted the use of both Canadian and American iron and steel in construction, rather than mandating exclusively US-produced materials.

Trump framed the decision as a betrayal of American workers and industry.

'What does the United States of America get - Absolutely NOTHING!' he wrote.

He also accused Canada of broader economic hostility, citing trade disputes and market access issues.

'The Tariffs Canada charges us for our Dairy products have, for many years, been unacceptable, putting our Farmers at great financial risk,' Trump said.

The bridge will provide another link between one of the busiest points on the U.S.-Canadian border. About a third of all trade between the US and Canada occurs between Detroit and Windsor. 

Trump's warning immediately triggered alarm among Michigan officials and lawmakers, who warned that blocking the bridge could devastate regional economic growth. 

Democratic Michigan Senator Elissa Slotkin condemned the threat, saying it would hurt American workers and businesses.

'Canceling this project will have serious repercussions. Higher costs for Michigan businesses, less secure supply chains, and ultimately, fewer jobs,' Slotkin said in a statement.

She accused Trump of undermining American interests in pursuit of political retaliation.

'With this threat, the president is punishing Michiganders for a trade war he started,' she said. 'Canada is our friend - not our enemy.'

Slotkin added: 'And I will do everything in my power to get this critical project back on track.' 

She said the Canadian-funded project is a 'huge boon' to her state and its economic future. 

'You´ll be able to move cargo from Montreal to Miami without ever stopping at a street light, so to shoot yourself in the foot and threaten the Gordie Howe Bridge means that this guy has completely lost the plot on what's good for us versus just what's spite against the Canadians,' Slotkin explained.

The Gordie Howe International Bridge, named after a Canadian hockey star who played for the Detroit Red Wings for 25 seasons, spans the Detroit River, connecting southwest Detroit with Windsor, Ontario.

It is expected to open later this year after years of construction and political wrangling.

Once operational, it will serve as a major commercial artery, providing direct access to Interstate 75 and Interstate 96 in Michigan and Highway 401 in Ontario—critical routes for cross-border trade between two deeply intertwined economies.

The project was negotiated by former Michigan Governor Rick Snyder - a Republican - and paid for by the Canadian government to help ease congestion over the existing Ambassador Bridge and Detroit-Windsor tunnel. Work has been underway since 2018.

The crossing will also become the largest land port of entry between Canada and the United States, standing roughly 150 feet above the river and rising to 720 feet at its tallest towers.

Approximately 6,000 commuters are expected to travel across the bridge daily, while commercial traffic is projected to reshape supply chains between the two countries.

The project is overseen by the Windsor-Detroit Bridge Authority and was negotiated under a 2012 agreement between Canada and Michigan.

Under that deal, Canada agreed to finance the entire construction cost, with plans to recoup its investment through toll revenues once the bridge opens.

Michigan, a swing state that Trump carried in both 2016 and 2024, has so far largely avoided the brunt of his second-term crackdown, which has targeted blue states with aggressive immigration raids and cuts to federal funding for major infrastructure projects.

Trump and Democratic Governor Gretchen Whitmer have also maintained an unusually cordial relationship, with the president publicly praising her during an Oval Office appearance last April. 

The two also shared a hug last year ahead of Trump's announcement of a new fighter jet mission for an Air National Guard base in Michigan.

While Canada paid for the project, the bridge will be operated under a joint ownership agreement between Michigan and Canada, said Stacey LaRouche, press secretary to Whitmer.

'This is the busiest trade crossing in North America,' LaRouche said, saying the bridge was 'good for Michigan workers and it's good for Michigan's auto industry' as well as being a good example of bipartisan and international cooperation.

'It's going to open one way or another, and the governor looks forward to attending the ribbon-cutting,' LaRouche said.

Rep. Shri Thanedar, the Democratic House representative of Detroit, said blocking the bridge would be 'crazy' and said Trump's attacks on Canada weren't good for business or jobs. 

'The bridge is going to help Michigan's economy. There's so much commerce between Michigan and Canada. The'´re one of our biggest partners,' Thanedar said.

Democratic Rep. Debbie Dingell of Ann Arbor brushed aside the president's threat, saying she's looking forward to the bridge's opening later in the spring. 'And I´ll be there,' Dingell said.

'That bridge is the biggest crossing in this country on the northern border. It's jobs. It's about protecting our economy. It was built with union jobs on both sides,' said Dingell. 'It's going to open. Canada is our ally.'

Trump's threat comes as the relationship between the US and Canada increasingly sours during the president's second term. 

The United States-Mexico-Canada trade agreement is up for review this year, and Trump has been taking a hard-line position ahead of those talks, including by issuing new tariff threats. 

Canadian Prime Minister Mark Carney, meanwhile, has spoken out on the world stage against economic coercion by the United States.