President Donald Trump’s trade adviser Peter Navarro expressed regret Tuesday for having said there is “a special place in hell” for Canadian Prime Minister Justin Trudeau.

“Let me correct a mistake I made,” Navarro said at a Wall Street Journal conference, according to video provided by the Journal’s CFO Network. “In conveying that message I used language that was inappropriate.”

Trump was furious after Trudeau had said at the end of a contentious economic summit in Quebec that he wouldn’t let Canada be pushed around in trade relations with the United States.

Appearing on “Fox News Sunday,” Navarro said: “There’s a special place in hell for any foreign leader that engages in bad faith diplomacy with President Donald J. Trump.”

The United States has alienated Canada and other allies by imposing tariffs on steel and aluminum imports, arguing that they pose a threat to U.S. national security. The move has been roundly criticized by Canada and the European Union, leading to heightened tensions at last week’s summit of the Group of Seven wealthy democracies — just before Trump left for Singapore and a meeting with North Korean dictator Kim Jong Un.

Trump’s top economic adviser, Larry Kudlow, suggested that Trump saw Trudeau as trying to weaken his hand before the summit with Kim. Kudlow said the president won’t “let a Canadian prime minister push him around. … Kim must not see American weakness.”

Kudlow later suffered a “very mild” heart attack, the White House said Monday, but was in good condition.

On Tuesday, Trump kept up the attack on Trudeau. At a news conference after his meeting with Kim, the president said the Canadian leader must not have realized that Trump had televisions on Air Force One, allowing him to monitor Trudeau’s news conference at the end of the G-7 summit.

“That’s going to cost a lot of money for the people of Canada; he learned,” Trump said wagging his finger. “You can’t do that.”

A spokeswoman for Trudeau, Eleanore Catenaro, declined to comment on Navarro’s acknowledgement of a mistake.

Bruce Heyman, a former U.S. ambassador to Canada, said:

“Navarro himself crossed a line, basically telling a leader of a foreign nation that he needs to go to hell. …I don’t care how mad, how angry you are, you don’t treat the head of state of another country like that unless you are getting ready for a military engagement of some kind.”

Heyman waged a campaign on Twitter to persuade Navarro to apologize by saying he was contacting U.S. politicians about his remarks.

(AP)