As the G20 summit began in Argentina on Friday, the USA president told reporters that the deal "changes the trade landscape forever".
Rota told CKAT that Canada's big concern is the tariffs on aluminum and steel which haven't been lifted yet by the U.S.
Trudeau described last week's factory cuts by General Motors as a "heavy blow".
But Mr Trudeau said there was still work to be done and called for United States tariffs on steel and aluminium to be scrapped.
Trump praised the deal in the lavish language he uses when touting one of his administration's accomplishments.
The deal still needs to be approved by Congress, but Trump said that he doesn't "expect to have much of a problem" getting that accomplished.
Canada has repeatedly referred to the new trade deal as the "New NAFTA" rather than USMCA.
The negotiations were long and at times acrimonious, with Freeland and her delegation learning first-hand what it's like to negotiate with President Donald Trump's administration, in particular his trade emissaries - U.S. Trade Representative Robert Lighthizer and his deputy, C.J. Mahoney.
'The new agreement will assure a new prosperity, ' he added. The three leaders then signed the monumental trade pact.
And the legislative bodies in each nation will have to ratify the treat.
It also includes measures that prohibit the ability of countries to import goods produced by forced labor.
Uncertainty would have only worsened and caused additional economic damage had the deal not been reached, Trudeau added.
Despite the symbolism of Friday's signing, Trump has no meetings with Trudeau scheduled while the two are in Argentina.
A particular sore point for the Canadian prime minister are the United States tariffs on steel and aluminium imposed earlier this year and he said these should be removed.
There are a few areas still to iron out. The deal will require ratification by all three countries' legislatures before taking effect.
NAFTA was signed by Canada, Mexico, and the United States in 1993 and came into force in 1994, during the presidency of Bill Clinton.
'A vast number of technical details need to be scrubbed and wrapped up, ' Freeland said.
Mexico's President Enrique Pena Nieto, who awarded Jared Kushner, Trump's son-in-law and adviser, with Mexico's highest order for foreigners, was warmer.
Trudeau and Trump discussed their plans for the G20 summit in a November 27 phone call, according to the White House. So important. I'm honored to be here with president Enrique Peña Nieto, become a great friend of Mexico, and Prime Minister Justin Trudeau who has also become a great friend. Canada has said it will lift its tariffs once the USA lifts its own.
Trump spent more than a year pushing the leaders of Canada and Mexico into agreeing to a rewrite of North American trade rules. 'The Prime Minister also reinforced the importance of both countries lifting the tariffs on steel and aluminum'.
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