The White House did not say what the president would talk about.
"Now, if we're unable to make a deal, we'll terminate NAFTA", Trump told reporters.
President Trump proposed a major shakeup of the world's economic order during a summit in Canada this week, suggesting the world's big economies drop all tariffs and market-distoring subsidies and go to a fully free system of trade.
Morneau said the tariff retaliation would cause "increasing friction" that would impede progress on NAFTA, but added there is a need "to step back from that destructive action so that we can actually get to the real work".
Trump, who argues his tariffs are meant to protect USA industry and workers from unfair worldwide competition, told reporters he had suggested to the other G7 leaders that all trade barriers, including tariffs and subsidies, be eliminated.
Last month, Trump violated and withdrew from the Iranian nuclear agreement, going against the wishes of the rest of the P5+1 (China, France, Russia, Germany, and the United Kingdom) countries who are all signatories to the deal. "They understand. They're trying to act like, "Well, we fought with you in the wars" but they don't mention the fact that they have trade barriers against our farmers, they don't mention the fact that they're charging nearly 300-per-cent tariffs".
The German statement seems to fly in the face of what Trump said in his closing press conference in Quebec where he vowed to ramp up combative trade actions - even against some of his country's closest allies - or curtail trade altogether if partners can not agree to more favourable terms for America.More news: Enzo Perez replaces Manuel Lanzini in Argentina squad
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Seven world leaders are meeting in Canada for the G7 summit over the weekend, and the official group photo shows the awkwardness of the circumstances.
President Donald Trump says re-admitting Russian Federation to a club of industrialized nations would be good for all countries. German Chancellor Angela Merkel sat between Macron and Trump on a sofa, while Trudeau sat to the left of the US president.
Trump said they are based on legitimate national security concerns, and he said he stood firm against the concerns of his fellow G7 leaders during their talks. "I would say the relationship is a 10".
The EU said it will impose the "rebalancing" tariffs on about $3.3 billion (2.8 billion euros) worth of US steel, bourbon, agricultural products including sweet corn, orange juice, cranberries and certain clothing made of cotton.
But I feel really confident", Trump said of Monday's meeting, which is the first between a North Korean leader and sitting US president, "It's never been done, It's never been tested.
Despite earlier reports of a rant over trade from Trump, he said the meeting "was not contentious" and called the relationships between the leaders "outstanding".
Canada and the European Union have denounced the US tariffs as illegal and unjustified and Ottawa has proposed levies on a range of USA goods next month while the European Union has pledged its own retaliatory measures.
In response, the European Union is preparing new tariffs set to hit USA exports ranging from jeans to bourbon whiskey.