Washington (CNN) President Donald Trump's chief economic adviser Larry Kudlow on Sunday accused Canadian Prime Minister Justin Trudeau of undermining the US and its allies with comments he made at the G7 summit.

"It was a betrayal," Kudlow said on CNN's "State of the Union."

Kudlow was speaking following the G7 summit in Canada on Saturday. As Trump flew from the summit with US allies to a planned meeting with North Korean leader Kim Jong Un in Singapore, he lashed out at Trudeau for what he said were his "false statements" at a news conference and said the US would not endorse the G7 communique, a negotiated statement on shared priorities among the group.

Although it is unclear which of Trudeau's statements Trump was calling false, Trudeau said in the news conference Saturday that Canada will "move forward with retaliatory measures" on July 1 in response to the Trump administration's decision to impose tariffs on steel and aluminum imports from Canada, the European Union and Mexico.

"I have made it very clear to the President that it is not something we relish doing, but it something that we absolutely will do," Trudeau said. "Canadians, we're polite, we're reasonable, but we also will not be pushed around."

In his interview Sunday, Kudlow accused Trudeau of making his comments for "domestic political consumption" and doing "a great disservice to the whole G7."

"He really kind of stabbed us in the back," Kudlow said.

Kudlow said the US had spent the summit negotiating in "good faith" with Trudeau and the other assembled leaders, and that the US had planned to sign the communique until Trudeau's news conference, which Kudlow called a "sophomoric play."

Peter Navarro, Trump's trade adviser, directed a series of stinging comments at Trudeau 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."

Navarro added that while these were his own words, they reflected the "the sentiment that was on Air Force One." Navarro also said Trump attending the G7 in Canada was a "courtesy" to Trudeau and that the President had "bigger things on his plate" in Singapore.

"He did him a favor," Navarro said. "He was even willing to sign that socialist communique."

Asked about the scathing comments from Trump's advisers on Sunday, Canadian Foreign Minister Chrystia Freeland called Trump's tariffs on Canadian aluminum and steel "illegal and unjustified" and said Canada does not believe in using "ad hominem attacks" on the international stage.

"Canada does not conduct its diplomacy through ad hominem attacks," Freeland said. "We don't think that that is a useful or productive way to do business, and perhaps we refrain particularly from ad hominem attacks when it comes to our relationship with our allies."

Kudlow: Partially about North Korea

Kudlow also said Trump's planned meeting with Kim was part of the reason why they were taking such issue with Trudeau's comments and 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," Kudlow said.

Kudlow said allies should have been more supportive of Trump given the meeting with Kim, using the words "crazy nuclear tyrant" in reference to the North Korean leader.

"They should have said to him, 'God speed, you are negotiating with the crazy nuclear tyrant in North Korea, and we are behind you,'" Kudlow said.

Trump, en route to Singapore, called Trudeau's news conference "very dishonest & weak" following his tweet ahead of the G7 summit calling Trudeau "indignant."

In response to Trump's tweets on Saturday, Trudeau's office contended that the Canadian leader said nothing he had not said previously "both in public and in private conversations" with Trump.

German Foreign Minister Heiko Mass said Trump's decision on the G7 communique was "actually not a real surprise" and cited Trump's previous decisions to remove the US from the Paris Climate Agreement and the Iran nuclear deal.

"In a matter of seconds, you can destroy trust with 280 Twitter characters," the German foreign minister added.

Criticism from senators

Trump's decision not to endorse the G7 communique brought pushback from some in the US, including Arizona Republican Sen. John McCain, who broke with Trump on Twitter.

"To our allies: bipartisan majorities of Americans remain pro-free trade, pro-globalization & supportive of alliances based on 70 years of shared values," McCain wrote. "Americans stand with you, even if our president doesn't."

Asked about the criticism from McCain, Kudlow said Trump had spent much of the summit advocating trade policies McCain would support.

"President Trump is essentially doing what John McCain wanted him to do with respect to free trade," Kudlow said. "President Trump made it clear, time and again, in those two days outside of Quebec that he wants to reinstitute a process of free trade, no tariffs, no tariff barriers, no quotas and subsidies."

California Democratic Sen. Dianne Feinstein, in a separate interview on the same CNN program, called Trump's decision not to sign the communique a "big mistake" that distanced the US from its top allies.

"I understand the President was upset," Feinstein said. "The President could have said that, but to walk away from our allies in this way, I think, is a mistake."