The last time the two North American leaders crossed paths, they started off with a warm handshake. But within hours Donald Trump had lashed out at Justin Trudeau, calling the Canadian prime minister “meek and mild” and accusing him of dishonesty.

On Wednesday Trudeau and Trump will again meet at the Nato summit in Brussels, for the first time since the last month’s ill-tempered G7 gathering in Quebec.

While they have spoken by phone since then, there’s little to suggest tensions have abated. This month, Canada launched tit-for-tat tariffs against the Americans in the first volley of a trade war between longstanding allies, while on Tuesday Trudeau asserted that Canada had no intention of meeting Trump’s demands that it meet Nato’s benchmark for defence spending.

“We’ve got ourselves in a knife fight with a real estate billionaire and we’re not equipped for that,” said John Higginbotham, a senior fellow at Ottawa’s Carleton University and the Centre for International Governance Innovation. “Relations are at as negative a time as I have ever seen, and I’ve been involved in Canada-US relations for about 40 years.”

Domestic politics is fuelling some of this confrontation, said Higginbotham, describing Trump’s attacks on Canada and Trudeau as “raw meat” for his Republican base.

But Trudeau has also benefited from the clash, with a recent poll suggesting that the majority of Canadians approved of Trudeau’s assertion after the G7 that Canada “will not be pushed around” by the US on trade, despite Trump citing the remarks as the source of his anger.

While the Brussels summit will focus on Nato, every interaction between Trump and Trudeau will be interpreted in the context of the tense renegotiations of Nafta, said Dan Ujczo, an Ohio-based trade lawyer with Dickinson Wright.

“We can ill afford a bad moment at the Nato summit between Prime Minister Trudeau and President Trump,” said Ujczo. “We don’t need any awkward handshakes or snubs or anything like that.”

When it comes to Nafta, much is at stake for Canada; the agreement underpins the three-quarters of Canada’s exports that go to the US and roughly 2.5m Canadian jobs that depend on American trade. The Bank of Canada warned earlier this year that uncertainty over Nafta has dampened business investment in Canada.

“I really hope Prime Minister Trudeau resists the temptation to join in with European allies and elsewhere to scold the United States,” said Ujczo. “Because we predict that this is going to be a pretty heated atmosphere.”

Canada’s approach to the Trump administration to date has sought to strike a balance between pursuing a constructive approach to negotiations while also defending Canadian interests, said Roland Paris, a University of Ottawa professor who served as foreign policy adviser to Trudeau during the prime minister’s first months in office.

“It’s obviously difficult with such an irascible partner in the White House, who can launch off on Twitter attacks seemingly without provocation,” he said. “I think that every country in the world is trying to figure out how to manage this unpredictable man.”

Canada’s approach to the Trump administration, which has also included an outreach campaign to a wide-ranging network for political and industry contacts, continues to be the right one, he argued.

“It’s not just a matter of a charm offensive and win him over and secure a deal – and then it hasn’t happened so it has failed – it’s a matter of managing a very complicated and difficult situation that is changing,” he said. “And the current situation is not good for Canada, but preventing it from getting worse should be the priority.”