US and Canadian trade negotiators had done their best on Friday afternoon to insist that a deal on Nafta remained on the table, even as they announced a five-day break in negotiations.

Then on Saturday, while Washington was gripped by the funeral for John McCain, Donald Trump, the US president who was not invited to attend the service, lashed out at his northern neighbours on Twitter. 

“We shouldn’t have to buy our friends with bad Trade Deals and Free Military Protection!,” Mr Trump wrote. “There is no political necessity to keep Canada in the new Nafta deal. If we don’t make a fair deal for the US after decades of abuse, Canada will be out. Congress should not interfere w/ these negotiations or I will simply terminate Nafta entirely & we will be far better off.”