The first iteration of Nafta was the Free Trade Agreement, signed between the United States and Canada in 1988, six years before the accord was expanded to include Mexico. Since then, the Canadian economy has become so intertwined with its larger American neighbor to the point that three-quarters of Canadian exports go across the border.

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But times have changed since Nafta abolished the high tariffs of 30 years ago. The later agreement that created the World Trade Organization has reduced tariffs to the point that even without Nafta, the majority of goods crossing the Canadian-American border would not face significant price increases.

Economists at the Royal Bank of Canada predicted that the cost to Canada’s economic growth of leaving Nafta — based on tariffs alone — would lower Canada’s economy by about a 1 percent spread over 5 to 10 years.

However, the true strength of Nafta for Canada’s economy has been the international investment it draws. That is why Canadian negotiators have always been insistent on maintaining the deal’s procedures for appealing American trade actions against Canada, and why Prime Minister Trudeau has called Mr. Trump’s demand that any new agreement contain an expiration date an absolute deal-breaker for his country.

“That gives international businesses assured market access, which is key to making Canada an attractive place to invest to serve the North American market,” said Dan Ciuriak, the former deputy chief economist in Canada’s foreign affairs and trade department. “For business, uncertainty is a cost.”

In the tentative deal announced Monday, both the United States and Mexico agreed to a type of expiration clause, reviewing the pact every six years that would extend its lifetime for 16 more years, officials said.

Whether the extension of an expiration date will appease Canadian negotiators is unclear. Trump administration officials said the tariff appeals process had been removed from the tentative trade agreement with Mexico. Canada is highly unlikely to accept that omission because its creation was the dealmaker for the original Free Trade Agreement.