Gov. Janet Mills gives the State of the Budget address at the State House in Augusta in January. Mills and five other Northeastern governors have invited the premiers of six Canadian provinces to a summit to discuss President Donald Trump’s tariffs. Shawn Patrick Ouellette/Portland Press Herald

Maine Gov. Janet Mills and five other Northeastern governors have invited the premiers of six Canadian provinces to a summit to discuss President Donald Trump’s tariffs and preserving strong trade relationships.

Mills joined Massachusetts Gov. Maura Healey, New York Gov. Kathy Hochul, Connecticut Gov. Ned Lamont, Rhode Island Gov. Daniel McKee and Vermont Gov. Phil Scott in inviting the premiers of New Brunswick, Newfoundland and Labrador, Nova Scotia, Ontario, Prince Edward Island and Québec to meet in Boston in the near future.

All are Democrats except Scott. New Hampshire Gov. Kelly Ayotte, also a Republican, did not sign the invitation.

“Canada is Maine’s single largest trading partner, with more than $6 billion in cross-border commerce occurring last year alone. Our economies and our cultures have enjoyed strong relationships for generations, which is now strained by the president’s haphazard tariffs and harmful rhetoric targeting our northern neighbors,” Mills said in a written statement.

Mills has been critical of Trump’s tariffs on Canada, which she believes will drive up the cost of heating oil, gasoline, food and more. Canada is Maine’s biggest trading partner by far, and many communities also have deeply held cultural relationships that are in jeopardy.

“Maine’s economic and commercial relationship with Canada is far deeper than with other international markets,” said Wade Merritt, president of Maine International Trade Center. “It’s best described as ‘making things together’ with a high degree of integration in natural resource-based industries like potatoes, blueberries, lobster and forest products. In addition, many manufacturing businesses across Maine rely on Canadian steel and aluminum to keep their factories running and workers on the job. Although previously announced tariffs are paused, significant uncertainty remains due to increased costs and the threat of retaliation.”

In addition to the impact on trade, Mills has warned that tariffs — combined with the president’s rhetoric about Canada — will negatively affect the upcoming summer tourist season. State officials have estimated that Maine could see about 225,000 fewer Canadian visitors this summer — about 25% less than last year.

“Canada has long been a vital part of Maine’s travel market. For generations, we’ve warmly welcomed Canadian visitors — whether they come for vacations, to see family and friends, or to enjoy shopping and entertainment,” Carolann Ouellette, director of the Maine Office of Tourism, said in a written statement.

“We acknowledge the concerns some of our Canadian friends may have about traveling to the U.S. right now,” Ouellette added. “Whether Canadians decide to visit this summer (and we truly hope they do) or at a later time, they will always find a warm welcome in Maine. Maine continues to invite travelers from Canada to experience all that our state has to offer — this year and for many years to come.”