President Donald Trump is using smoke from Canada’s wildfires to threaten tariffs.

Trump lashed out at Canada in a post on Truth Social on Friday, accusing the United States’ northern neighbor of mismanaging its forests and causing the current outbreak of wildfires that are sending waves of smoke into the United States.

“America is being unnecessarily invaded by dirty, polluted, unhealthy air, the quality of which is dangerous and totally unacceptable!” Trump wrote, adding: “The cost is incalculable!”

The president said it was becoming an annual occurrence and was costing the United States billions, although it is unclear what that figure was based on. He said the cost of pollution must be added to the tariffs Canada is already paying.

Wildfires in parts of central Canada have sent thick smoke across the Midwest and Northeast this week, causing high levels of air pollution, including in Washington, DC.

Republican lawmakers have blamed Canada’s forest management practices for the smoke plumes and are pressuring the country to act.

Sen. Bernie Moreno, R-Ohio, said he would introduce a bill next week to sanction Canada and its government officials, and shared a post about air pollution in Cleveland. Rep. Nick Langworthy of New York said he was reaching out to Canadian officials to encourage them to act.

“Canada must take meaningful action to prevent these catastrophic wildfires and protect both Canadians and Americans,” he wrote in X. “If it refuses to do so, there should be consequences.”