It was all smiles as Justin Trudeau welcomed the US president to the G7 summit but mutual goodwill appears to be at a low ebb

Shortly after he landed on Canadian soil for the first time as president, Donald Trump was warmly greeted by Justin Trudeau and his wife, Sophie Grégoire Trudeau.

The trio lingered on the podium, chatting comfortably as they posed for photos at the start of the G7 summit in Quebec.

There was little hint of the acrimony that had filled Trump’s Twitter feed hours earlier as he had raged at Canada and its prime minister, laying bare escalating trade tensions that have seemingly pushed US-Canada relations to their lowest point in recent memory.

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Since taking office, Trump has routinely disparaged Canada’s trade policies, calling them a “disgrace” and “unfair”. As he prepared to visit Canada this week, however, the US president took it up a notch, personally attacking Trudeau.

“Prime Minister Trudeau is being so indignant, bringing up the relationship that the U.S. and Canada had over the many years and all sorts of other things,” Trump tweeted on Thursday. “But he doesn’t bring up the fact that they charge us up to 300% on dairy – hurting our Farmers, killing our Agriculture!”

Trump escalated his attacks at the end of the G7 summit on Saturday when he blamed Trudeau for the US pulling out of the official communique, calling the Canadian PM “weak and dishonest”.

The tweet was part of tumultuous 24 hours or so in which Trump mused about terminating the North American Free Trade Agreement (Nafta), the pact that underpins roughly 2.5m Canadian jobs and the three-quarters of Canadian exports that go to the US, and railed at Canada’s use of import tariffs and production controls to protect its dairy sector.

Play Video 1:12 Justin Trudeau's G7 comments that angered Donald Trump – video

After an election campaign in which Trump had focused his antipathy on Mexico – vowing to build a billion-dollar wall, crack down on immigration and impose a steep border tax – many Canadians had not expected to find their country in the US president’s crosshairs.

Trump’s increased targeting of Canada appeared to begin earlier this year when he sought to portray it as a country of suave swindlers, said Christopher Sands, director of the Center for Canadian Studies at Johns Hopkins University.

“We lose a lot with Canada. People don’t know it. Canada is very smooth,” Trump told a gathering of state governors in February. “They have you believe that it’s wonderful. And it is. For them – not wonderful for us … So we have to start showing that we know what we’re doing.”

The comments hinted at the fact that Canada’s strategy of crisscrossing the US to reinforce to senators and governors how Americans benefit from their relationship with Canada was having an impact, said Sands.

“That kind of annoyed Trump,” he said. “I don’t think he loves Trudeau but I think that early on they had a good rapport. Now he finds that Trudeau is undermining him in his own turf.”

Trump to Trudeau in testy tariff call: 'Didn't you guys burn down the White House?' Read more

Trade tensions escalated after the US announced an end to Canada’s exemption on steel and aluminum tariffs, one week after a reportedly testy phone call between the two leaders, in which Trump referenced the 1814 burning down of the White House by British troops to justify levying the tariffs against Canada on national security grounds.

Canada countered with retaliatory measures on C$16.6bn ($12.8bn) worth of goods and a tougher line from Trudeau. After more than a year of carefully avoiding any criticism of the US president, Trudeau slammed the president’s decision. “We have to believe that at some point their common sense will prevail,” he told reporters. “But we see no sign of that in this action today by the US administration.”

He also stopped by American television to make it clear that Canada found the tariffs “insulting”. But the TV appearance further stoked the president’s ire, said Sands. “I don’t think he’s become public enemy number one by any stretch, but he has sort of annoyed Trump.”

The result is the kind of sparks that have probably existed between US and Canadian leaders throughout history, but which are rarely aired in public, said Sands. “Nixon famously called Justin Trudeau’s father an asshole and Trudeau zinged back – but it was all behind the scenes and it came out years later.”

Others contextualised the rhetoric by pointing to the scramble to renegotiate Nafta.

“It is all posturing within the context of the Nafta negotiations,” said Dunniela Kaufman, a Canadian trade lawyer based in Washington. “I think Trump thought that he would arrive and the Canadians would play ball, that they would negotiate with him and get to where they needed to get.”

But the talks have stalled after the Canadians refuse to budge on two key issues: a sunset clause that would allow any of the signatories to quit the pact after five years and binding dispute mechanisms.

Trump had hoped the US metal tariffs would force Canada’s hand. Instead the country shot back with retaliatory measures, she said. “So I think he’s frustrated that Canada didn’t do that.”

Officials on both sides of the border have downplayed any notion of a feud brewing between the longstanding allies. “I regard this as much like a family quarrel,” Larry Kudlow, Trump’s chief economic adviser, told reporters this week. “I’m always the optimist, I believe it can be worked out, and I’m always hopeful on that point.”