President Donald Trump's trade policy adviser, Peter Navarro, apologized Tuesday for his "inappropriate" comment suggesting that "there's a special place in hell" for Canadian Prime Minister Justin Trudeau.

"Let me correct a mistake I made," Navarro told the audience at the Wall Street Journal's annual CFO Network conference. "In conveying that message, I used language that was inappropriate and basically lost the power of that message. I own that, that was my mistake, those were my words."

Asked if he were apologizing to Trudeau, he responded, "Yeah, absolutely."

Over the weekend, in an interview on "Fox News Sunday," he 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."

The harshness of the language drew fire from many members of Congress, including key Republicans.

"It’s uncalled for. Just absolutely uncalled for," Sen. Cory Gardner, R-Colo., said Monday.

"I’m pretty sure that circles of hell are not reserved for Canadians proposing retaliatory tariffs," Sen. Ted Cruz, R-Texas, added.

In striking such a hostile tone against one of the oldest and closest U.S. allies, Navarro said Tuesday he was emboldened to send a "strong signal of strength" on the eve of the landmark summit between Trump and North Korean leader Kim Jong Un.

Trudeau angered the president for comments he made in a news conference at the conclusion of the G7 meeting, during which he said that the "U.S. Tariffs were kind of insulting" and Canada "will not be pushed around" by the United States.

Those remarks then sparked a Twitter outburst from Trump in which he called Trudeau "so indignant."

Trump addressed the feud following his meetings with Kim in Singapore at a more than hour-long press conference. He was asked why he was jeopardizing relations with long-standing allies like Canada while welcoming a historical U.S. enemy with open arms as a friend.

"I left the [G7] meeting and I'll be honest, we are being taken advantage of by virtually every one of those countries, very, very seriously," Trump said. "Now, the United States because of bad management at the top, because of presidents that didn't care about trade or didn't understand it or whatever reason, for many years with China being obviously the most successful at it but the European Union is second, 151 billion we lost, they were represented at the meeting, and we're being taken advantage of on trade. Canada does have very big advantages over us in terms of trade deficits. We have a big trade deficit with Canada. I was riding where, oh, it's actually a surplus."

He then asserted multiple times to the room full of reporters that he has a "good relationship" with Trudeau.

"I have a good relationship with Justin Trudeau," he said. "Other than he had a news conference that he had because he assumed I was in an airplane and I wasn't watching. He learned. That's going to cost a lot of money for the people of Canada. He learned. You can't do. We laughed. We had a very good relationship. I've had a good relationship with Justin."

In Canada Tuesday, commenting on the Trump-Kim summit, where the two leaders appeared very cordial and even smiling together, Trudeau said he supported Trump's efforts to reach a nuclear deal.

"Obviously we support the continuing efforts by the President on North Korea," the Canadian prime minister said. "We look forward to looking at the details of the agreement."

But asked about the rhetoric coming from the White House, Trudeau stood firm on his commitment to first safeguard Canadian interests.

"On his comments, I am going to stay focused on defending jobs for Canadians and supporting Canadian interests."

ABC News' Ali Rogin contributed to this report.