Donald Trump always needs an opponent.

At the moment that opponent is the unlikely figure of Canada's Prime Minister, Justin Trudeau.

If he were a coffee or cigarette brand, Trudeau would surely be marketed as smooth and mild.

Yet the US President and his aides have lashed the leader of America's neighbour, longtime ally, Five Eyes member and G7 Summit host with language usually reserved for rogue nations just before the bombs begin to fall.


Ironically, it is instead just before Trump meets Kim Jong Un, the leader of North Korea - a member of former US President George W. Bush's "Axis of Evil" in 2002.

The Trump Administration's surreal mugging of Trudeau is a coordinated all-in maul.

Trump kicked it off yesterday with tweets calling the Prime Minister "dishonest and weak".

Trudeau had said Canada will retaliate against the Trump Administration's plan to impose tariffs on steel and aluminum imports from Canada, the EU and Mexico.

Trudeau added: "Canadians, we're polite, we're reasonable, but we also will not be pushed around."

Trump thundered on Twitter: "PM Justin Trudeau of Canada acted so meek and mild during our @G7 meetings only to give a news conference after I left saying that, 'US Tariffs were kind of insulting' and he 'will not be pushed around.' Very dishonest & weak. Our Tariffs are in response to his of 270% on dairy!"

Today the President's advisers ran with the ball.

Trump trade adviser Peter Navarro said: "There's a special place in hell for any foreign leader that engages in bad faith diplomacy with President Donald J. Trump and then tries to stab him in the back on the way out the door...that's what bad faith Justin Trudeau did with that stunt press conference."

Trump chief economic adviser Larry Kudlow said: "He really kind of stabbed us in the back." Kudlow added that Trump was "not going to let a Canadian prime minister push him around" ahead of the North Korea summit. "He is not going to permit any show of weakness on the trip to negotiate with North Korea."

Note the reinforcement of 'stabbing in the back'.

This is both unprecedented language, in modern times, to use against Canada's leader and part of an ongoing pattern of behaviour with Trump.

He sets up straw men - whether they be liberal, establishment figures and their policies; immigrants; Mexicans; judges; cultural stars; protesting athletes - as bears to poke. He presents himself as the battler taking on a multitude of foes.

High-profile fights are a useful distraction from the Russia investigation and other problems.

And this regular stirring of outrage is Trump's way to keep his base on the bubble, and to keep the tribe tight as the Midterm elections loom. He needs high turnout and enthusiam to keep Congress in Republican hands. Gallup has Trump at 41 per cent approval and 55 per cent disapproval.

There's also a swaggering ego at the centre here: Trump has been talking about how he hasn't needed to prepare for his meeting with Kim and will 'know' almost instantly whether the North Korean is serious about the talks. "My touch, my feel - that's what I do," he said.

But in this case there is a timing issue.

Trump wants his summit with Kim in Singapore to be a stunning success to polish and hold aloft to the world.

Kudlow said, Trump doesn't want "any show of weakness," any publicly-stated attempt to "push him around" beforehand. Hence a bruised US ally.

As Macleans editor Scott Gilmore tweeted: "We may have reached a point where even when a new American President arrives, the western allies will not trust the US to lead again, nor even set the agenda".