President Donald Trump has threatened to block the opening of a bridge connecting the US and Canada until Washington is "fully compensated for everything" it has given to its northern neighbour.

The Gordie Howe International Bridge, connecting the Canadian province of Ontario to the US state of Michigan, would not open until Ottawa "treats the United States with the Fairness and Respect that we deserve", Trump wrote on social media.

According to the project's website, the bridge is being funded by the Canadian government but will be publicly owned by both Canada and Michigan.

Michigan Senator Elissa Slotkin, a Democrat, said closing the "incredibly important infrastructure project" would be "awful for our state's economy".

The move could have "serious repercussions" she said in a post on X: "Higher costs for Michigan businesses, less secure supply chains, and ultimately, fewer jobs."

It is not clear how Trump could block its opening but he said negotiations would begin immediately, without elaborating.

The bridge, which spans the Detroit River, is expected to open to traffic pending formal tests and approvals in the early part of this year. Construction began in 2018, but the project has been a point of contention between the countries for more than a decade.

It is estimated to have cost $6.4bn CAD (£3.4bn), according to the Canadian Broadcasting Corporation (CBC).

In the statement on his Truth Social platform, Trump said that the US should own "at least one half of this asset". He also suggested that Canada owned both the Canadian and US sides of the bridge.

The organisation developing the bridge, the Windsor-Detroit Bridge Authority, is wholly owned by the Canadian government, according to the project's website.

Trump wrote: "The Canadian Government expects me, as President of the United States, to PERMIT them to just 'take advantage of America!'"

"I will not allow this bridge to open until the United States is fully compensated for everything we have given them," he added.

He also blamed former President Barack Obama for allowing construction to begin without the use of any US steel.

But Mayor Drew Dilkens of Windsor, Ontario, on the Canadian side of the bridge, told the CBC that this accusation is wrong.

"It's just insane," he said. "I really can't believe what I'm reading."

The Moroun family - the American owners of the neighbouring Ambassador Bridge that also connects Detroit to Canada - appealed to Trump during his first term to stop construction of the new bridge, arguing that it infringed on their exclusive ability to collect tolls.

In response, Trump and then-Prime Minister Justin Trudeau issued a joint statement saying the bridge was a "vital economic link" between the countries.

Michigan's Democratic Governor Gretchen Whitmer pushed back on Trump's threat to close the bridge, saying it was good for jobs in her state.

"This project has been a tremendous example of bipartisan and international cooperation," Whitmer's press secretary Stacey LaRouche told the CBC.

Trump on Monday pointed to recent trade disputes between the two countries, saying that "the Tariffs Canada charges us for our Dairy products have, for many years, been unacceptable".

He also said that a trade deal signed between Canada and China last month would "eat Canada alive".

Trump continued: "The first thing China will do is terminate ALL Ice Hockey being played in Canada, and permanently eliminate The Stanley Cup."

But Slotkin hit back at this, saying the only reason Canada was on the verge of a trade deal with China was because Trump "has kicked them in the teeth for a year".

Canada is our friend, not our enemy, she added, promising to work to get the project back on track.

Canada's bridge authority, the Ontario premier's office and the Detroit mayor's office did not immediately respond to requests for comment.