OTTAWA -- Defence Minister Harjit Sajjan broke from the prime minister and foreign minister’s message track on Stephen Harper co-signing a full-page advertisement in Wednesday’s edition of the New York Times hailing U.S. President Donald Trump's leadership on Iran, saying it was out of line for the former prime minister to do so.

In an interview with Don Martin, host of CTV’s Power Play, Sajjan called it "not helpful," saying "a nation needs to speak with one voice, and Canadians have elected a government to speak on their behalf… and this doesn’t help, but this is not surprising, this is something that the Harper government has done in the past."

Harper was one of several former international leaders and diplomats that signed the full-page ad.

"Mr. President, you are right about Iran," the ad reads in big bold letters, followed by several paragraphs in which Harper, former Canadian foreign affairs minister John Baird, former Australian prime minister John Howard, and other former foreign ministers and military figures write that they stand in support of his decision to withdraw from the 2015 Joint Comprehensive Plan of Action (CJPOA) otherwise known as the Iran nuclear deal.

Sajjan referenced the ongoing NAFTA negotiations with the U.S. and Mexico as more reason for Canadians to present a united front on foreign issues.

"Having a former prime minister do something like this is not helpful," Sajjan said, adding that he believes it was out of line.

"Iran is a danger to us, to our allies, to freedom," the black and white ad reads. It was paid for by one of the signatories, Rafael L. Bardaji, who is director of World Wide Strategy, a consultancy firm based in Miami.

"An Islamist and revolutionary regime, such as the one that controls Tehran today, must never be allowed to possess a nuclear option -- not a bomb, not a path to a bomb, not a nuclear program with the slightest doubt of its extent and military applications," reads the ad.

PM, Freeland say Harper entitled to opinion

Trudeau addressed the ad Thursday at a press conference in Saguenay, Que., alongside Quebec Premier Philippe Couillard.

“Obviously Mr. Harper is a private citizen and is allowed his own opinions,” Trudeau said.

The prime minister said the Iran nuclear deal, which was negotiated under the Obama administration, was “not a perfect accord,” but that it was a positive step toward preventing Iran from developing nuclear weapons.

The Conservatives must now reckon with what to make of Harper’s views, Trudeau said.

“We are going to continue to insist that Canadian foreign policy will be established in Canada, and not in Washington or elsewhere around the world. And I think it’s a question for the current Conservative Party as to whether or not they agree with their former leader,” Trudeau said.

Foreign Affairs Minister Chrystia Freeland also addressed the ad on Thursday, saying that the government continues to support the agreement and that Harper is entitled to express his views.

Freeland said the primary issue between Canada and Iran is Iran’s refusal to allow widow Maryam Mombeini to leave the country. Mombeini’s husband died while in an Iranian prison earlier this year. Her sons say her passport was confiscated by Iranian officials when they tried to board a plane to Vancouver in March.

Conservative MPs who spoke with CTV News on Thursday said they had no issue with Harper doing so as a private citizen.

There is an online version of the advertisement that states the same message but provides no further information.

With files from CTV News' Graham Slaughter