CALGARY, Alberta — Canadian Prime Minister Mark Carney warned Thursday that the United States is trying to break Canada so it can “own us” as he urged oil-rich Alberta not to begin a process toward separation in Monday’s referendum.

The vote is not a direct referendum on independence. Alberta, which has the world’s fourth-largest proven oil reserves, will decide whether to remain a province or instruct the government to begin the legal process toward a future referendum on separation.

“This referendum comes at the worst possible time,” Carney told a large pro-Canada rally in Calgary. “The world has become more dangerous and divided. Some outside our borders are working to break us so they can own us.”

He did not directly mention the U.S. or its President Donald Trump in that passage, but has done so in similar past speeches. Carney’s warning came as U.S. President Donald Trump wages a trade war with Canada and after his repeated threats to make Canada the 51st U.S. state. Carney has argued that Canada needs to become more economically resilient and less dependent on the United States.

Carney urged Albertans not to use the vote simply to send Ottawa a message, saying a decisive result could settle the separation question.

“Don’t be fooled by the idea you can ‘send a message’ with your vote,” Carney said. “This is not poker. A vote against Canada is a dangerous bluff that will lead to years of deep division and great uncertainty.”

Carney, who grew up in Alberta, spent Thursday campaigning in Calgary before addressing the Forever Canadian rally at the BMO Centre. His office estimated about 5,000 people attended, with some waiting more than two hours to get through security. Organizers were also holding a second rally with Carney in Edmonton on Friday.

Earlier Thursday, he pointed to the many Albertans who were born or educated elsewhere in Canada and to firefighters who come from across the country to help Alberta during wildfires as examples of the ties binding the province to the rest of Canada.

At the rally, Carney also acknowledged the grievances that have fueled alienation in Alberta.

“The frustrations that many Albertans have felt are real,” he said. Carney said that while growing up, Ottawa made Albertans feel “like our resources weren’t our own” and that more recently the province was made to feel its energy contributions were “against the tides of history.”

The setting is striking for a Liberal prime minister. Alberta has spent decades feuding with Liberal governments in Ottawa, particularly over energy and federal power. But Carney has broken with some of the policies associated with his predecessor, Justin Trudeau, fast-tracked a proposed new oil pipeline to the Pacific and called Canada an energy superpower.

Carney pointed to the Pacific Link pipeline as evidence of a changed relationship, saying it would create more than 140,000 jobs and generate revenue for social programs.

His biggest cheer came when he said the pipeline would reduce Canada’s dependence on the United States.

“Careful, they might think that’s election interference. A little touchy,” Carney joked, drawing laughter. He was referring to U.S. Ambassador Pete Hoekstra’s warning to Canadian politicians not to interfere in the U.S. midterm elections.

Tanya Clemens, co-chair of the pro-independence group Let Alberta Decide, acknowledged Carney presents a challenge.

“He’s formidable for sure,” Clemens told The Associated Press.

Clemens argued, however, that Carney’s agreements with Alberta Premier Danielle Smith amount to “pinky promises” that do not resolve long-standing grievances with Ottawa.

Keith Wilson, another leader of Let Alberta Decide, rejected Carney’s argument that global instability made this the wrong time for the vote.

“The worst timing for this, why? I don’t understand what’s the logic,” Wilson said. “Then it’s the best time for him to get back to Ottawa.”

Wilson said Carney should ask Parliament to repeal federal measures that separatists say have hurt Alberta, including authority he says could be used to tax oil exports in retaliation against the United States. He predicted Carney would eventually impose such a tax despite Carney saying he sees no value in using Canadian energy exports as leverage against the U.S.

“It’s one cabinet meeting away,” Wilson said. “He’s gonna do it. He has to do it.”

Smith, who called the vote but supports remaining in Canada, cast her ballot Wednesday and said she voted for Alberta to remain in Canada. She has said support for separation remains too high for her liking.

“Canada can still work,” Smith said after voting. “We just need to make some changes.”

Daniel Béland, a political science professor at McGill University, called Carney’s popularity in Alberta “highly unusual” for a Liberal prime minister. He said Carney has also benefited from a “Trump effect,” as Trump’s trade war and 51st-state threats have rallied Canadians around their leader — even in Alberta.

The referendum marks a remarkable rise for a cause long relegated to Alberta’s political fringes. After the COVID-19 pandemic and the 2022 Freedom Convoy, activists who had organized against vaccine mandates and other restrictions turned their attention to Alberta independence.

The convoy began over vaccine requirements for cross-border truckers but grew into a broader protest against pandemic restrictions, paralyzing downtown Ottawa and blocking major Canada-U.S. border crossings.

Clemens said COVID accelerated the movement by teaching people how to organize politically and become more involved in party politics. She said separatists also see Monday’s vote not simply as a step toward independence but as a way to give Alberta leverage in negotiations with Ottawa.

Advance voting runs through Saturday, with the final vote Monday.