The American nations belong to the NAFTA and the US presidential hopeful Donald Trump has vowed to scrap the agreement.
The leaders of the United States, Canada and Mexico gather on Wednesday to stress the importance of trade at a time of mounting international doubts about the benefits of globalisation.
The three nations belong to the North American Free Trade Agreement (NAFTA), which US Republican presidential candidate Donald Trump on Tuesday vowed to renegotiate or even scrap if he wins power.
Trump says free trade has been disastrous for American workers, costing countless thousands of jobs and depressing wages. Similar complaints were heard in Britain ahead of a shock referendum vote last week to leave the European Union and its own free trade area.
"We've seen around the world many examples of protectionism, of concern, of stepping away from trade agreements," Canadian Prime Minister Justin Trudeau told reporters on Tuesday, stressing the need for more rather than less cooperation.
"Better partnerships are a path to prosperity and that's a compelling example that we want to showcase at a time where unfortunately people are prone to turning inwards, which will be at the cost of economic growth and their own success."
Trudeau, US President Barack Obama and Mexican President Enrique Pena Nieto will meet in Ottawa and are scheduled to hold a news conference at 3 p.m. (1900 GMT). The leaders, known informally as the Three Amigos, usually meet about once a year.
"We anticipate that leaders will spend a significant time talking about trade, for example, how to facilitate trade by automating our borders," US National Security Council official Mark Feierstein told reporters on Tuesday.
The trio will also discuss Britain's so-called Brexit vote, which wiped more than $2 trillion off global equity markets and dealt a huge blow to the EU. "The president will obviously want an opportunity to discuss ... how we may be able to coordinate our efforts to insulate ourselves to the extent possible," said Feierstein.
Earl Wayne, Obama's former ambassador to Mexico, said that amid increasing criticism of NAFTA, leaders had to find a better way to explain that up to 14 million US jobs depend on trade with Canada and Mexico.
"That's a hard story to tell," he told reporters. "There is a lot of skepticism, and it's easier to sell the negative arguments." The three men will also pledge to produce 50 percent of their nations' electricity from clean energy by 2025. Obama is due to address the Canadian Parliament at 5.25 p.m.
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