His remarks at the Ronald Reagan Presidential Library in Simi Valley, California, struck a cooperative tone at a time when President Donald Trump is threatening to withdraw from the 24-year-old pact that governs trade on the continent.
Trudeau said 9 million jobs in America are tied to trade and investment with Canada and "the truth is that both Canada and the United States are winning. And so is Mexico. And that's exactly how we should keep it."
But he also acknowledged that global trade is not working for everyone and said income inequality is growing worldwide.
"We need to collectively do a much better job of ensuring the benefits of trade are shared more broadly, to more people," he said.
He added: "President Trump and I agree about this: Too many people have been left behind, even as our economies surged."
The accord, he said, should be modernized with "a willingness to compromise on all sides."
Trudeau's stop at the hilltop library came during a swing through the U.S. in which he has warned Canada won't be muscled into a trade deal that is unfavorable to his country, and promoted Canada as a destination for California technology firms uneasy with shifting U.S. immigration policy.
The next round of talks over the trade pact in Mexico later this month have loomed over the visit, which also included stops in Chicago and San Francisco.
Trump called the agreement a job-killing "disaster" on the campaign trail. He has threatened to pull out unless the deal requires more auto production in the U.S., while shifting additional government contracts to U.S. companies.
In his speech, Trudeau made repeated references to the historic connections between the two countries and argued that backing away from NAFTA could unspool deep ties across the continent - with an unknown cost.
The location of the speech carried symbolic weight, alluding to the longstanding trade relationship between the U.S. and Canada. In 1988, Reagan and then-Prime Minister Brian Mulroney signed the first free trade agreement - a precursor to NAFTA.
"Let us not raise fresh barriers between our peoples," Trudeau said.
Earlier, Trudeau picked up promises of investments and jobs during his first official visit to San Francisco. Among them: Salesforce CEO Marc Benioff announced the online business software company will invest another $2 billion in its Canadian operations.
Uncertainty over Trump's immigration policies has provided momentum for Trudeau's economic pitch to Silicon Valley, where many companies that rely on foreign workers have become uneasy.
Trudeau promoted his country's fast-track employment permit for certain workers, dubbed the "global skills strategy visa."
Trudeau also met Thursday with Amazon Chief Executive Jeff Bezos as Bezos considers possible locations for a second headquarters. Toronto, which has created a government-sponsored innovation hub for tech companies, was the only one of several Canadian cities that made the shortlist.
Trudeau's stop in San Francisco highlighted the already strong ties between Canada and California, particularly in research, academia and technology.
While much of the attention on the North American Free Trade Agreement has focused on physical commodities such as vehicle manufacturing, dairy and timber, skilled workers have also become increasingly mobile between the U.S., Canada and Mexico.
Google built its latest DeepMind artificial intelligence facility at the University of Alberta in Edmonton, Canada.
The liberal Trudeau argued that differing political views need not stand in the way of trade agreement, citing a long history of the countries working together.
Reaching agreements has always required "persistence and no shortage of sunny, Reagan-esque optimism on both sides," he said.
Associated Press Writer Juliet Williams in San Francisco contributed.
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