In a radio interview on Wednesday, Mr. Trudeau described such a mechanism as a “red line” for his country.

“That ensures the rules are actually followed,” Mr. Trudeau told a radio station in Alberta, Canada. “We know we have a president that doesn’t always follow the rules as they’re laid out.”

Last week, the United States International Trade Commission overturned the Trump administration’s decision to impose tariffs on Canadian newsprint. The commission rejected the Commerce Department’s argument that imports of Canadian newsprint were harming American manufacturers and ordered that the tariffs be lifted.

Mr. Trudeau’s barb followed a barrage of criticism in the last week from Mr. Trump, who has accused Canada of unfair trade practices and threatened to cripple its automobile industry with tariffs. The president also repeated his threat to leave Canada from a revised Nafta and move ahead with just Mexico.

“There is no political necessity to keep Canada in the new NAFTA deal,” Mr. Trump said on Twitter on Saturday. “If we don’t make a fair deal for the U.S. after decades of abuse, Canada will be out.”

Like Mr. Trump, Mr. Trudeau also made clear on Wednesday that Canada was willing to walk.

“We’re not going to accept that we have to sign a bad deal just because that’s what the president wants,” he said. “We’ll walk away and not sign a deal rather than sign a bad deal for Canadians.”

Discussions between Canada and the United States ended last week without a deal, prompting Mr. Trump to inform Congress that he would move ahead with a trade pact with Mexico and give Canada the chance to remain in a revised Nafta “if it is willing.” Canada now has until the end of September to reach its own agreement with the United States, allowing the three-country pact to stay intact.