US President Donald Trump has threatened to impose new tariffs on Canada, blaming the country for wildfire smoke that has spread across parts of the northern United States.

Hundreds of wildfires in Canada have sent large amounts of smoke south of the border, creating poor air quality and covering several US cities in a thick haze.

Trump criticised Canada’s handling of the fires, describing the smoke as “filthy, polluted, and unhealthy air” and accusing Canada of “willful negligence”.

His comments came after US lawmakers raised concerns about the impact of the wildfires and the resulting air pollution. Ontario Premier Doug Ford, meanwhile, urged the US government to focus on providing assistance to fight the fires rather than criticising Canada.

The threat of new tariffs adds another layer of tension to relations between the two neighbouring countries, as officials continue to deal with the widespread wildfire emergency.

Canadian authorities and emergency crews are working to contain the fires, while smoke continues to affect air quality in parts of Canada and the northern US.