But tensions over tariffs, looming GM layoffs and questions about the pact's prospects in Congress clouded the celebratory moment.
Canada is confident it will win legal challenges to American steel and aluminum tariffs that remain despite the new NAFTA deal, Foreign Affairs Minister Chrystia Freeland said Friday in Buenos Aires following a high-profile signing ceremony for the trade treaty.
Legislatures from Mexico and Canada, as well as Congress, must approve the deal before it is finalized.
Overhanging the summit in Buenos Aires, the Argentine capital, is a trade dispute between the United States and China, the world's two largest economies, which have imposed tariffs on hundreds of billions of dollars of each other's imports.
BDI, Germany's main industry association, said in a statement that the autos rules of origin were "a retrograde step compared with NAFTA".
Canada Sanctions 17 Saudis in Khashoggi Death Ahead of G-20
Mohammed al-Otaibi, the Saudi consul-general to Istanbul at the time of the killing, is also among the 17 Saudis targeted. The government is still calling for a "transparent and rigorous" investigation into the death of the columnist.
Democrats have signaled they won't support the deal without additional protections for workers, though it calls for more safeguards than the agreement it would replace.
But the U.S. trade landscape will shift significantly in January when Democrats take control of the U.S. House of Representatives after winning midterm elections in November. "It's been so well reviewed I don't expect to have much of a problem".
USMCA puts in a 16-year "sunset" clause, i.e., the terms of the agreement expire after a set period of time.
For the record, the document's preamble refers to an "Agreement between the United States of America, the United Mexican States and Canada".
Nonetheless, the signing concluded an arduous process that was marked by repeated threats from Trump to exit the continent's free-trade zone.
Mexican negotiators reportedly desire modifications to limit future metal shipments to the United States to 80 percent of current levels, while Canada is resisting quotas in the face of cheap steel from China entering the American market.
The biggest changes target the auto industry.
Ukrainian president asks Trump to deliver pointed message to Putin
Trump is due to meet Putin on the sidelines of the G20 summit in Buenos Aires, which convenes on Friday and Saturday. But losses were limited by expectations that crude exporters would agree to cut output at an upcoming OPEC meeting.
The ceremonial signing does not mean the United States-Mexico-Canada Agreement - the USMCA, as it has been rebranded - will now go into effect.
But fundamental change happened under the deal's predecessor, the North American Free Trade Agreement.
"Donald, it's all the more reason why we need to keep working to remove the tariffs on steel and aluminium between our two countries", Trudeau said.
While Trump hailed the revised trade pact, Trudeau was more measured and used the event to call on Trump to remove the steel and aluminum tariffs the USA slapped on Canada and Mexico.
On his final day as Mexico's president before Andres Manuel Lopez Obrador is sworn in on Saturday, Pena Nieto said the trade agreement includes provisions for e-commerce and information technology.
Meanwhile, Mr Trump's other major trade-related meeting during the G20 summit will be with China's leader Xi Jinping on Saturday, with analysts looking for any sign that the USA president will hold off on plans to toughen United States tariffs on Chinese imports in January. Also of interest was whether Trump would have an encounter with Saudi Crown Prince Mohammed bin Salman, who was attending amid global dismay over the murder of Saudi journalist Jamal Khashoggi.
Van Bommel: We will go for the win against Barcelona
In this game, if Barca draws and Inter Milan fails to beat Tottenham , they advance and clinch the group. Barcelona was without the injured Luis Suarez , with Ousmane Dembele taking his place.