The leader of Canada’s Ontario province on Saturday lashed out at President Donald Trump over his threat to add “the cost of pollution” from that country’s wildfires to US tariffs.

Trump said Friday that he’s holding Canada responsible for wildfire smoke hovering over much of the Midwest and the eastern United States and vowed to call Prime Minister Mark Carney “to find out what they are doing about it.” He suggested that the cost of dealing with pollution from the fires that continued to blanket large swaths of the US on Saturday could be added to the tariffs that Canada is already paying.

“We are holding Canada responsible for the fact that they are not properly maintaining their Forests, and Brush therein, and the United States is being unnecessarily invaded by filthy, polluted, and unhealthy air, the quality of which is dangerous, and totally unacceptable!” Trump wrote in a Truth Social post.

On Saturday, Doug Ford, the premier of Ontario, where there are 191 active wildfires, expressed frustration with Trump’s comments. He noted that Canadian rescue workers helped fight wildfires in Southern California last year.

“I find it a shame the administration in the US and Congress people (are) writing these letters and blaming us,” Ford said during a news conference. “They have a very short, short memory. We had the water bombers, everyone ready, going over to California. It was last year.”