United States President Donald Trump has threatened to impose additional tariffs on Canada, accusing the country of failing to manage the wildfires that have sent thick smoke across parts of the United States.
The warning came as hundreds of active wildfires continued to burn across Canada, with many concentrated in Ontario and a significant number remaining out of control.
Trump said he would hold Canada responsible for the deteriorating air quality affecting US cities and indicated that the economic cost of the smoke would be added to existing tariffs on Canadian exports.
Canadian officials, meanwhile, defended their response and emphasized continued cooperation with the United States in combating the fires.
Trump accused Canada of failing to properly maintain its forests and brush, describing the situation as "Willful Negligence" and saying he planned to raise the issue with Prime Minister Mark Carney.
The latest threat adds to ongoing trade tensions between the two countries, where tariffs have already been used by the US administration to press Canada on a range of issues.
Republican lawmakers also criticized Canada's wildfire policies, arguing that recurring smoke has affected public health and economic activity in the United States.
Ontario Premier Doug Ford rejected those criticisms, saying Canada has consistently supported the United States during natural disasters and urging American officials to send assistance rather than complaints.
Ford said firefighters, aircraft and emergency resources remain deployed across affected regions while several communities have been evacuated.
Canadian officials said the two countries remain in close contact through long-standing emergency cooperation agreements and stressed that wildfire response is a shared effort.
Prime Minister Carney said climate change is a responsibility shared by all countries, including the United States.
Canadian ministers also pointed to investments in forest sustainability and wildfire prevention while emphasizing that the fires pose a cross-border challenge.
Scientists cited in the source material said wildfire activity has been driven by sustained hot, dry weather, below-average rainfall and other environmental factors, with smoke moving according to wind patterns regardless of national borders.
Experts also said improved forest management can reduce risk in some areas but cannot prevent fires across Canada's vast remote landscapes.
The dispute unfolded as wildfire smoke prompted widespread air quality concerns across parts of the northern United States while firefighting operations continued across Canada.