The United States, Canada, and Mexico signed a North American trade pact on November 30, with President Donald Trump brushing aside concerns that he could face difficulties getting the deal through the US Congress.
Trump himself acknowledged that it hadn't been easy, but said "battles sometimes make great friendships".
While praising the "historic" nature of the deal, Trudeau also told Trump that the progress gave "all the more reason why we need to keep working to remove the tariffs on steel and aluminium between our countries".
Trump, Prime Minister Justin Trudeau and outgoing Mexican President Enrique Pena Nieto signed an authorization for the deal on Friday morning in Buenos Aires on the sidelines of the Group of 20 summit, with their ministers signing it shortly after.
A day before Canada, the United States and Mexico are due to sign a new trade pact, negotiators are still thrashing out what exactly they will be putting their names to, officials said on Thursday. But they also cited steel and aluminum tariffs as a lingering problem. His agenda Friday also includes meetings with the leaders of Japan and India, the signing of a revamped trade deal with Canada and Mexico, as well as a number of heavily choreographed group activities for the gathering of leaders of rich and developing nations. Elizabeth Warren, D-Mass., a likely Democratic presidential candidate, said Thursday that she would oppose the trade pact as inadequate for American workers, foreshadowing a possible 2020 campaign plank.
'The new agreement will assure a new prosperity, ' he added.
Despite Trump's hostile rhetoric about unauthorized immigrants crossing into the United States from Mexico, he appeared to be on better terms with that nation's president, Enrique Peña Nieto, who was serving his final day in office - and, in Trump's view, going out on a high note by signing the trade agreement.
The deal - 32 chapters, 11 annexes and 12 side letters - sets new rules for the auto sector, including a higher threshold for North American content and rules requiring 40 per cent of vehicle parts be made by workers paid at least $16 an hour.
Trudeau has shown contempt for the USMCA name, saying sarcastically at a Toronto business convention in October that the new name made a "big" difference in its quality.
Trump said negotiating the deal known in Washington as the US-Mexico-Canada Agreement, or USMCA, had seen the leaders take "a lot of barbs and a little abuse". "It's great for all our countries".
The new agreement doesn't lift the tariffs on steel and aluminum, with both the Mexican and Canadian governments stating their displeasure that the issue has not yet been solved.
Meanwhile, the deal still needs to be ratified by lawmakers in all three countries.
"Not only have they conceded market access but they have also gone along with the U.S.to ensure we can not be competitive on any world markets where the U.S.is present", said David Wiens, vice-president of Dairy Farmers of Canada. That could prove to be a hard task in the United States, especially now that Democrats - instead of Trump's Republicans - will control the House of Representatives come January.
As the G20 summit began in Argentina on Friday, the U.S. president told reporters that the deal "changes the trade landscape forever".
For a auto to receive duty-free treatment, 75 percent of its parts have to be manufactured in North America.
"This New NAFTA is a huge missed opportunity", said Karen Hansen-Kuhn, director of Trade and Global Governance at the Institute for Agriculture and Trade Policy. "That should be true for NAFTA and true for every deal we cut".
For starters, US -imposed tariffs on steel and aluminum exports remain in place against both Canada and Mexico, as do a raft of countermeasures.