"Let me correct a mistake I made", White House economic advisor Peter Navarro was quoted as saying at a Washington event organized by The Wall Street Journal.
Trump took time at his news conference to explain a photo that went viral from the G7 summit.
Mr. Trump called Trudeau "very dishonest & weak" for his objections to the US tariffs.
He called Mr Trudeau "dishonest & weak" after Mr Trudeau said at a news conference that Canada would retaliate for new U.S. tariffs. Trump tweeted on Saturday.
"Canadians. stood shoulder-to-shoulder with American soldiers in far-off lands in conflicts from the First World War onward", Trudeau said Saturday at a press conference, The Washington Post reported.
White House economic adviser Larry Kudlow on Sunday also accused Trudeau of having "stabbed us in the back" and engaging in a "sophomoric, political stunt for domestic consumption".
Foreign Affairs Minister Chrystia Freeland said Sunday that "Canada does not believe that ad hominem attacks are a particularly appropriate or useful way to conduct our relations with other countries".
Asked if these were statements from the President, Navarro said they were his words, but that they reflected "the sentiment that was on Air Force One". "He'll learn, he can't do that", Mr Trump said.
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Howard was insistent that the game will be fully playable offline, but he also said that "every surviving human is a real player". It seems that you are going to get the complete role-playing experience with this game, but everything is optimized for mobile.
On Tuesday, Trump said: "We have a big trade deficit with Canada.it's close to $100 billion a year deal loss".
Navarro's apology was unusual in that President Donald Trump and his aides have seldom walked back harsh and even incorrect statements.
Canada's approach has been to hope for the best outcome but to always be prepared for the worst, and "to have a plan B, C, D, E and F and maybe to the end of the alphabet", Freeland said.
President Donald Trump took more swipes at Canada and its prime minister over trade issues as he settled in for a summit with North Korea in Singapore, contending that "Fair Trade is now to be called Fool Trade if it is not Reciprocal".
The decision to back out of the communique was "in large part" because of the upcoming North Korea summit, Kudlow said.
At a news conference Tuesday after his summit with North Korean leader Kim Jong Un, Trump recounted his recent tough exchanges with Trudeau. "The Prime Minister said nothing he hasn't said before - both in public, and in private conversations with the President".
"That's going to cost a lot of money for the people of Canada".
Trump lashed out against Trudeau on Twitter, doubling down on tariffs recently placed on Canadian imports and slamming what he sees as an unequal trading relationship between the two countries.
He said, "Yes, absolutely".