President Donald Trump has threatened to block the opening of a $4.7 billion bridge connecting Detroit, Michigan, to Windsor, Ontario, in the latest display of frayed relations between the U.S. and Canada.

In a lengthy social media post, Trump raised a number of issues against his northern neighbor and doubled down on his often-cited claim that Canada has “treated the United States very unfairly for decades.”

The President claimed that Canada will own both sides of the Gordie Howe International Bridge, for which construction began in 2018 and is nearing completion, and complained that the infrastructure has been built with “virtually no U.S. content.”

After accusing Ontario of refusing to stock some U.S.-produced alcoholic products in shops and complaining about Canada’s tariffs on dairy products, Trump declared he will “not allow this bridge to open until the United States is fully compensated” for everything it has “given” to Canada.

“We will start negotiations immediately,” he warned. “With all that we have given them, we should own, perhaps, at least one half of this asset.”

The Canada-Michigan Crossing Agreement, signed in June 2012, states that the Canadian government will pay for the bridge, and use toll funds—collected over 30 years—as reimbursement.

The agreement also stipulates that the bridge, named after prolific Canadian ice hockey player Gordie Howe, will be publicly owned by the governments of Canada and Michigan, and all iron and steel used in construction will be sourced from either the U.S. or Canada. The offer from the Canadian government to cover most of the costs was accepted by Michigan’s then-Gov. Rick Snyder.

All seemed to be going well in February 2017, when Trump and then-Canadian Prime Minister Justin Trudeau released a joint statement, celebrating the project and calling the crossing “a vital economic link between our two countries.”

More recently, the U.S. Department of Homeland Security (DHS) published a rule on Jan. 30, declaring the bridge will serve as an official port of entry. It said the crossing will save $12.7 million annually for travelers, in part by reducing congestion.

Trump’s new threat to suspend the bridge’s opening has prompted criticism among Canadian officials.

“It’s just insane. When I read that post, I really can’t believe what I’m reading,” Mayor of Windsor Drew Dilkens told CBC, adding that the bridge should create an opportunity “where a Prime Minister would meet a President in the middle, they would shake hands, and they would celebrate this victory for two nations. Unfortunately, Donald Trump has created an environment where I don’t think that is going to happen in the near term.”

Trump’s frustration over the bridge marks the latest tension between the President and Canada.

At the World Economic Forum in Davos in January, Trump told attendees that Canada “lives because of the United States.” In a filmed address from Québec City, Carney responded to the claim, firmly stating: “Canada does not live because of the United States. Canada thrives because we are Canadian.”

Trump had lashed out at Canada after taking umbrage at Carney’s own Davos speech, during which he boldly stated that the old world order is “not coming back.” He encouraged people not to “mourn” the way things used to be and advised that “nostalgia is not a strategy.” Carney urged middle powers to stand up for themselves, accusing “great powers” of using economic pressure to yield results.

While he did not name the U.S. or its President, Carney’s speech came in the midst of Trump attempting to acquire Greenland and after long-repeated threats to annex Canada and make it the “51st state.”