Canadian Prime Minister Mark Carney has told the US to "start being serious" about trade talks, days before Canada is due to hit back against Donald Trump's tariffs with retaliatory duties of its own. The row has intensified after the collapse of US-Canada negotiations, with Trump signing an executive order to rename Lake Ontario "Lake America" and his trade representative dismissing the dispute as "more their emergency than ours" – comments Carney branded beneath the dignity of US officials.

The US has imposed 50% tariffs on $20bn of Canadian goods, and Canada, its second-largest trading partner, plans retaliatory tariffs on an equivalent value of American goods from 8 September, a move likely to raise prices for US consumers. US trade representative Jamieson Greer blamed Canada for the breakdown, citing demands such as lighter taxes on heavy-duty trucks, while Canadian officials pointed instead to confusion within the White House over who was leading the talks. Carney also said US negotiators had treated Canada's use of the French language as an "irritant", insisting such rights were non-negotiable in Quebec, as Trump continued to claim Canada wants the benefits of US statehood without joining.