Trump also slammed Europe, writing, "the USA pays close to the entire cost of North Atlantic Treaty Organisation - protecting many of these same countries that rip us off on trade".
"Sorry, we can not let our friends, or enemies, take advantage of us on Trade anymore".
Press secretary Sarah Huckabee Sanders also referred to discussions between Trump and Trudeau on a "bilateral deal".
Before the apology, some US lawmakers on Tuesday questioned the strong language the White House and Trump have used toward Canada in contrast to the praise he gave North Korea at Tuesday's summit in Singapore. "Obviously, we don't want to be held hostage to these tariffs Donald Trump has arbitrarily put in place, but there are other things that we would like to see in terms of advancing the free trade agenda".
Mulroney, who has a personal relationship with Trump and has been quietly advising the prime minister on how to deal with the mercurial USA president, likened Trump's weekend tirade to "serious summer squalls". "We just shook hands!"
Among the many topics the president addressed with reporters afterward was his recent Twitter campaign against Trudeau, whom he has called "dishonest" and "weak".
White House trade adviser Peter Navarro apologised today for his sharp comments directed at Canadian Prime Minister Justin Trudeau after last week's Group of Seven summit, according to the Wall Street Journal.
The president has barely disguised the real reason for these trade actions, tweeting most recently that, "Our Tariffs are in response to his (Canada's) of 270% on dairy!"
President Trump responded with a tweet calling Trudeau "very dishonest and weak" and followed up by saying the U.S. would not endorse the G7 communique, a document signed by the seven leaders underlining their commitment to free and open trade.
"What I saw Prime Minister Trudeau say was, I thought, fairly benign and certainly didn't warrant any attack".
"There's a special place in hell for any foreign leader that engages in bad faith diplomacy with President Donald J. Trump", Navarro insisted. Mr Trump said the move would protect domestic producers that were vital to U.S. security.
"It is something that we have discussed and Canada is certainly prepared for any eventuality", Freeland said.
"Canada does not conduct its diplomacy through ad hominem attacks".
"Divisive rhetoric and personal attacks from the USA administration are clearly unhelpful", he added.