Trudeau told the media he waited until Tuesday to apologize for his remarks because he "wanted to make sure that I had the chance to express directly to leaders in the Ukrainian community ... how seriously the Liberal party takes the situation in Ukraine."
He added that his joke during a pre-taped appearance on a Radio-Canada current affairs program "made light of some very real fears and concerns that Ukrainians have about Russian intervention."
Trudeau apologized earlier in the day to the Ukrainian ambassador to Canada after making a quick visit to the embassy. Vadym Prystaiko, who had called for the apology a day earlier, praised Trudeau for being the first Canadian politician to sign a book of condolences.
The Liberal leader also took to Twitter to say he'd made amends with Paul Grod, head of the Ukrainian Canadian Congress.
In his interview last Thursday with "Tout le Monde en Parle," Trudeau suggested Russia, peeved about being eliminated from the medal round in Olympic hockey, might vent spleen by getting involved in Ukraine.
"It is even more worrisome now," Trudeau said in the interview, broadcast Sunday night. "Especially since Russia lost in hockey, they will be in a bad mood. We are afraid of a Russian intervention in Ukraine."
"Only because of hockey?" the show's host, Guy A. Lepage, asked Trudeau as other panelists chuckled.
"No," Trudeau replied. "It is an attempt to bring a light view of a situation that is extremely serious and extremely troubling."
In the aftermath of Trudeau's comments, both the Conservatives and NDP pounced in an effort to inflict some damage. Trudeau is consistently ahead in public-opinion polls and wrapped up a successful policy convention in Montreal over the weekend.
In the last year, Trudeau's political foes have taken aim at his remarks on China. At his joke about used-car salesmen. At his comments following the Boston marathon bombings. And now on Ukraine.
And yet Trudeau is still comfortably atop the polls.
Tory insiders say it's just a matter of time before Trudeau's verbal missteps start to hurt him, and the current Conservative strategy is to simply bide their time until he does himself in.
NDP strategists insist they're focused on Harper, not Trudeau.
Nonetheless a party insider implicitly praised the Tories in an off-the-record conversation Tuesday when he pointed out that Trudeau's proposals on the Ukraine during the same Radio-Canada interview last week were decidedly similar to what the Conservatives had announced earlier in the day.
One political observer says even if both parties work together in the shadows to undermine Trudeau, the Tories and the NDP may be waiting a long time for his implosion.
"There is a kind of gravity-defying quality to this situation," said Richard Johnston, a public-opinion expert at the University of British Columbia.
"The question that's consuming them is figuring out how to take him down ... There is a high-wire act element with Justin Trudeau, to be sure, but so far he's managing to pull it off. He seems to have pretty good instincts, and there's smart people around him keeping him on track."
Steve MacKinnon, a political consultant at Hill and Knowlton and a former Liberal party official, says the Tories are flailing in their attempts to attack Trudeau.
"The danger is more on the Conservative side; they're dealing with someone they don't know how to deal with," MacKinnon said in an interview.
"He's connecting with people, and people see a human being there, and they seem to be quite prepared to allow him to say things in unconventional ways. The Conservatives don't know how to attack him and it just underscores their inability to connect. It boomerangs on them."
Harper did his best in question period on Tuesday, mocking Trudeau for failing to hold a post-convention media availability as the event wrapped up on Sunday.
"I do not recall ever having to leave one of my conventions through the back door," Harper said to cheers and a standing ovation from his caucus.
Trudeau, who has pledged to stay above the fray in terms of attack politics, nonetheless got in a shot of his own at Harper, saying he doesn't need any lessons from the prime minister on judgment.
"I'm quite pleased that I will be up against someone who had the judgment to decide that Pat Brazeau, Pam Wallin and Mike Duffy were suitable members of our Senate," he said outside the House of Commons, repeating a line from his weekend speech in Montreal.
"I am confident that my values, my approach and my openness with Canadians is exactly what people from across the country are looking for."
Follow Lee-Anne Goodman on Twitter at @leeanne25