In one new feature, it requires that 40 percent of cars' contents eventually be made in countries that pay autoworkers at least $16 an hour - that is, in the United States and Canada and not in Mexico - to qualify for duty-free treatment.
The pact will lock in US market access to Canada and Mexico, expand American exports and includes new measures to ensure fair competition, explained Trump as he stood alongside Canadian Prime Minister Justin Trudeau and Mexican President Enrique Pena Nieto.
Democratic Rep. Jan Schakowsky of IL, for one, said ahead of the signing that it does "not do almost enough to raise wages for workers, lower costs for healthcare consumers, or protect the environment", and that barring major changes, the deal "will result in more broken promises by Donald Trump to American workers".
The signing ceremony took place on the sidelines of the G20 summit in Buenos Aires.
The US-Mexico-Canada Agreement is meant to replace the 24-year-old North American Free Trade Agreement, which Trump has long denigrated as a "disaster".
"President, I must say Pena Nieto, and Prime Minister Trudeau, we've worked hard on this agreement", Trump said. All of our countries will benefit greatly.
Top US officials were on hand for the signing, including Secretary of State Mike Pompeo, Treasury Secretary Steven Mnuchin, national security adviser John Bolton and the President's daughter Ivanka Trump and son-in-law Jared Kushner.
That could prove to be an overly optimistic assessment.
If approved, it would likely take effect around the start of January 2020. The side letters also include deals between the USA and Mexico on biologic drugs, cheese names and auto safety standards; and deals between the us and Canada on wine, water and energy.
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Canada and Mexico are the second and third-biggest U.S. trading partners, each accounting for more than $500 billion in trade per year, nearly rivaling China and the 28 European Union member states combined.
As The Globe and Mail reported previously, the United States has been pressing Mexico behind the scenes to allow the Trump administration to decide how much production from each company would be protected in the event of future tariffs.
Mexican President Pena Nieto, on his last day in office, called the revamped version of NAFTA important in shoring up "the view of an integrated North America with the firm belief that together we are stronger and more competitive".
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.
"As a result (of the new agreement), the tariff-free access NAFTA guaranteed for more than 70 per cent of Canada's total exports is secure".
"Canadians got here because Team Canada was driven by the interests of the middle class", Trudeau said.
The U.S. agreed to Canada's insistence that the dispute settlement system - formerly known as Chapter 19 - remain in the deal.
Trump did not refer to General Motors' recently announced plans to cut jobs at five American factories, four in the United States and one in Canada, but Trudeau did, calling it a "heavy blow".
"Make no mistake, we will stand up for our workers and fight for their families and communities", added Trudeau. The vast majority of the pact still needs to be ratified by lawmakers in the three countries but the signing enacts a handful of immediate protections, such as from auto tariffs. Trump had commented how the US did not like Canada's negotiation style.
As of last week, Shonk said neither the USA government, nor the Mexican government, made an effort to remove that language from the agreement.