Open this photo in gallery:

B.C. Premier David Eby addresses reporters on Wednesday after a first ministers meeting. Mr. Eby says it’s inappropriate to ‘ask for assistance to break up this country from a foreign power.’Justin Tang/The Canadian Press

British Columbia Premier David Eby says Alberta separatists who went to Washington in search of political support are engaged in treason and he will be raising the matter at Thursday’s first ministers meeting in Ottawa.

Mr. Eby was referencing a report in the Financial Times, which said U.S. President Donald Trump’s administration held covert meetings with Alberta separatists.

Open this photo in gallery:

Jeffrey Rath at the United Conservative Party’s annual general meeting in November.Amber Bracken/The Globe and Mail

Jeff Rath, legal counsel of the Alberta Prosperity Project, told the FT the separatist group met with U.S. State Department officials in Washington in April and are seeking another meeting next month.

“To go to a foreign country and to ask for assistance of breaking up Canada, there’s an old-fashioned word for that, and that word is treason,” Mr. Eby said. “It is completely inappropriate to seek to weaken Canada, to seek to go and ask for assistance to break up this country from a foreign power.”

Mr. Eby said Canadians need to speak with one voice on the issue.

U.S. Treasury Secretary Scott Bessent weighed in on Alberta separatism last week, calling the Western province “a natural partner for the U.S.”

A referendum on Alberta independence could happen later this year if a group of residents can collect the nearly 178,000 signatures required to force a vote on the issue. That group, Stay Free Alberta, has until early May to gather support for the vote.

Alberta Premier Danielle Smith did not stop to speak with reporters Thursday on her way into the meeting.

Mr. Rath told The Globe and Mail in an interview last week that he and his colleagues have twice met with U.S. State Department officials and they’re planning a February meeting with the U.S. Treasury.

Mr. Rath has broadly advertised his contact with the State Department, saying their meetings with U.S. officials have not discussed statehood. He has declined to share who he has specifically met, arguing he’s not obligated to share those details as a private citizen.

Most recently, Mr. Rath has said he and his colleagues are seeking a $500-billion line of credit from the U.S. government. The U.S. Treasury told the FT that no commitments have been made.

The U.S. State Department confirmed the meetings to The Globe and sent a statement, which was attributed to a senior official who was not named.

“The Department regularly meets with civil society types. As is typical in routine meetings such as these, no commitments were made,” they wrote.

Ontario Premier Doug Ford, who told reporters Wednesday that it would be a disaster for Canada if the sovereigntist Parti Québécois is elected in Quebec’s scheduled fall election, appealed for Canadian unity on Thursday morning.

“You know, we have a referendum going on out in Alberta. The separatists in Quebec say they’re gonna call a referendum if they get elected. Like, folks, we need to stick together. It’s Team Canada. It’s nothing else,” he said.

Open this photo in gallery:

Saskatchewan Premier Scott Moe on Thursday called for a measured response when asked about U.S. officials meeting with Alberta separatists.Adrian Wyld/The Canadian Press

When asked about the United States engaging with Alberta’s separatist movement, Saskatchewan Premier Scott Moe said Canadians should be measured in their response.

“We need to just take a breath when those comments are made,” he said, adding that the U.S. is Canada’s largest trading partner. “Having a war of words back and forth is not going to put us in a better bargaining position by any stretch.”

New Brunswick Premier Susan Holt said she’s confident most Albertans want to remain in Canada.

“I think you’re talking about a minority of people who are agitating and I am very optimistic that the majority of Albertans will demonstrate their love for this country and their desire to be a part of it,” she said.

Once the premiers were seated for Thursday’s meeting, Mr. Carney delivered opening remarks to the group before the session was closed to the media.

He said they will be discussing efforts to expand Canadian trade with the United States and other international partners.

“Today, we’ll discuss how we can co-ordinate all of those efforts on trade and inbound investment to maximize their impact,” he said.

He also said they will work on reducing internal trade barriers within Canada.

“A number of you have already made significant progress,” he said, singling out Mr. Ford and Nova Scotia Premier Tim Houston.

“We all know that more can be done. To realize our full potential, we need to break down the remaining costly and longstanding barriers once and for all,” he said.

Mr. Carney said they will also be discussing efforts to move ahead on major new infrastructure projects “from every region of the country.”