Former Prime Minister Brian Mulroney says Prime Minister Justin Trudeau “did the right thing” by signing a new North American free trade agreement on the sidelines of the G20 Summit in Buenos Aires, Argentina.

“When somebody gives you a document that you agree with and says, ‘This is NAFTA,’ you sign. You don’t horse around,” Mulroney said Saturday in an interview with CTV News’ Sandie Rinaldo. “He did the right thing," Mulroney added.

Mulroney also said Trudeau made the right move by signing the deal before controversial American steel and aluminum tariffs on Canada were lifted.

“We’ll get rid of the tariffs,” Mulroney predicted. “They’ll come off. In fact, I’m sure he’s working on them down there in Buenos Aires."

Mulroney oversaw negotiations on the original NAFTA deal between Canada, the U.S. and Mexico.

On Saturday, Conservative Leader Andrew Scheer criticized Trudeau, saying on Twitter that the signing ceremony was the prime minister’s “final capitulation to Donald Trump ... even while steel and aluminum tariffs remain.”

Mulroney said the Canada-United States-Mexico Agreement (CUSMA) is “a good deal for Canada.

“Could it be better?” he said. “Sure. Did he give up something? Sure he did. But so did the Americans. They wanted Chapter 19 out, and the Canadians said, ‘Over our dead bodies,’ as I told (former U.S. president Ronald) Reagan.”

Chapter 19 refers to the original NAFTA’s dispute-resolution mechanism.

Mulroney said the new deal is by no means perfect, “but it’s hell of a lot better than not having one at all.”

Mulroney: Trudeau ‘has a tougher challenge’

Trudeau’s new mission, Mulroney said, will be to ease the tensions between Ottawa and Washington that arose during negotiation. Mulroney, who is said to have a personal relationship with the mercurial U.S. president, is confident that that will happen.

“The hostility … that we saw between the president and the prime minister will dissipate in the fullness of time,” he said. “And our prime minister will have an occasion to re-establish the relationship on a basis that it ought to be,” he added.

In addition to preserving national unity, maintaining positive Canada-U.S. relations is one of the most important parts of a prime minister’s job, Mulroney opined.

“You need a congenial type in the White House to help you along,” he said. “I definitely had that, and I can’t say that’s always the case these days, so that’s why I sympathize with Justin, the prime minister, that he has a tougher challenge than some of us had.”