There is a "special place in hell" for Canadian Prime Minister Justin Trudeau because of his decision to slam the U.S. in a post-G7 press conference, White House Director of Trade Policy Peter Navarro said on "Fox News Sunday."

"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," Navarro said. "And that's what bad faith Justin Trudeau did with that stunt press conference. That's what weak, dishonest Justin Trudeau did. And that comes right from Air Force One."

Later Sunday, top European Union official Donald Tusk tweeted an apparent rebuke of Navarro. Trump has imposed steel and aluminum tariffs on both the EU and Canada because of what he has called their unfair trade practices.

“There is a special place in heaven for @JustinTrudeau,” Tusk, the president of the EU's European Council, wrote. "Canada, thank you for the perfect organisation of G7!”

The dustup began shortly after Trump left the G7 summit, where the world leaders had reached a tentative agreement on a joint statement. While Trump was departing Canada, Trudeau held a press conference in which he said that Canada will not be "pushed around" by the U.S. and called Trump's tariffs "unjust."

"There's a special place in hell for any foreign leader that engages in bad faith diplomacy with President Donald J. Trump." — White House Director of Trade Policy Peter Navarro

Navarro reiterated that his sentiment was shared onboard Air Force One after the summit, as it headed toward Singapore for the planned meeting between Trump and North Korean leader Kim Jong Un.

WATCH: TRUMP SAYS US IS LIKE 'PIGGY BANK THAT EVERYONE IS ROBBING' ON TRADE

"And I'll tell you this, to my friends in Canada, that was one of the worst political miscalculations of a Canadian leader in modern Canadian history," Navarro continued. "All Justin Trudeau had to do was take the win. President Trump did the courtesy to Justin Trudeau to travel up to Quebec for that summit. He had other things, bigger things on his plate in Singapore.

"And what did Trudeau did -- do as soon as -- as soon as the plane took off from Canadian airspace, Trudeau stuck our president in the back. That will not stand."

Navarro called Canada's high tariffs on American dairy products, and planned retaliatory tariffs, an "attack on our political system."

"And as far as this retaliation goes, the American press needs to do a much better job of what the Canadians are getting ready to do because it's nothing short of an attack on our political system and it's nothing short of Canada trying to raise its high protectionist barriers even higher on things like maple syrup and other goods," Navarro said.

Also on Sunday, top White House economic adviser Larry Kudlow said Trudeau "stabbed us in the back" with a "double cross" at the G7 summit.

In a fiery interview, Kudlow called Trudeau's press conference a "sophomoric, political stunt for domestic consumption."

“President Trump played that process in good faith," Kudlow said on CNN's "State of the Union" Sunday. "So, I ask you: He gets up in the airplane and leaves, and then Trudeau starts blasting him at a domestic news conference? I am sorry, that’s a betrayal. That’s a double cross.”

In the air at the time of Trudeau's press conference, Trump tweeted: "Based on Justin's false statements at his news conference, and the fact that Canada is charging massive Tariffs to our U.S. farmers, workers and companies, I have instructed our U.S. Reps not to endorse the Communique as we look at Tariffs on automobiles flooding the U.S. Market!

He followed up by tweeting: "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!"

