US President Donald Trump has threatened to impose new tariffs on Canada over the impact of smoke from hundreds of wildfires burning across the country.
Trump says the smoke has caused what he described as an incalculable cost to the United States.
The smoke has spread across several cities, including New York and Washington DC, where poor air quality has prompted health warnings.
Many of the wildfires remain out of control, forcing evacuations and destroying homes and infrastructure, although Canadian officials say fire activity in Ontario is beginning to ease.
Source: BBC News
