AP via CP President Donald Trump (C) Prime Minister Justin Trudeau, and Mexico's President Enrique Pena Neto, left, participate in a signing ceremony for a new trade on Nov. 30, 2018 in Buenos Aires, Argentina

BUENOS AIRES, Argentina — Signing on to a revamped NAFTA alleviates the serious economic uncertainty that lingered throughout the negotiating process, Prime Minister Justin Trudeau said Friday while flanked by U.S. President Donald Trump and outgoing Mexican President Enrique Pena Nieto at a highly-anticipated formalizing of the trade pact in Buenos Aires. Uncertainty would have only worsened and caused additional economic damage had the deal not been reached, Trudeau added. "The new North American free trade agreement maintains stability for Canada's entire economy, stability that's essential for the millions of jobs and middle class families across the country," he said. "That's why I'm here today."

The signing ceremony at a packed hotel in Buenos Aires on the sidelines of the G20 summit did not come without a fight. The U.S.'s punitive tariffs on steel and aluminum from other countries remain in place, along with stiff countermeasures from Canada and Mexico. As negotiations to remove those tariffs dragged on in the past few weeks, Canadian officials and emissaries insisted Canada would not take part in a fanfare-filled signing affair until the levies were lifted. All that changed this week, said one insider: "At the end of the day, removing the uncertainty from the rest of the economy is too important to pass up." During his remarks, Trudeau made a point of nudging Trump to remove the tariffs. "There's much more work to do in lowering trade barriers and in fostering growth that benefits everyone," Trudeau said. Battles sometimes make great friendships, so it is really terrific.U.S. President Donald Trump "As a result, the tariff-free access NAFTA guaranteed for more than 70 per cent of Canada's total exports is secure. That's essential for businesses, families, jobs, entrepreneurs, and hardworking people in every corner of our country. " Trudeau raised the tariff issue before the three leaders emerged together for the signing ceremony, said officials in the Prime Minister's Office. A Canadian official also said earlier Friday that the big advantage of signing onto the agreement now is a side letter on the auto industry exempting Canada of potential tariffs on exports of up to 2.6 million vehicles — well above current levels. At the beginning of his remarks, Trump also acknowledged the process to negotiate the United States-Mexico-Canada agreement has been "a battle." "Battles sometimes make great friendships, so it is really terrific," Trump said. Friday marked an important deadline for the trade pact because a new Mexican president takes over Saturday who might not honour the tentative deal struck by his predecessor.

SAUL LOEB via Getty Images Prime Minister Justin Trudeau and U.S. President Donald Trump are pictured at a signing ceremony for a new trade deal between the U.S., Canada and Mexico.

Trump acknowledged that Friday was Pena Nieto's last day in office and congratulated him on the achievement of signing on to the deal. The signing of the three-way trade pact is largely ceremonial because it still needs to be ratified by all three countries before it can formally take effect. U.S. lawmakers have already indicated they don't expect to tackle the USMCA — or CUSMA, as Ottawa now calls it — until after the new Congress is sworn in early next year. 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 car parts be made by workers paid at least $16 an hour. It preserves a contentious dispute-resolution system the U.S. dearly wanted gone, extends patent protections for biologic drugs and allows U.S. farmers a 3.6-per-cent share of Canada's famously guarded market for poultry, eggs and dairy products — a concession that dismayed Canadian dairy producers. Earlier this month, a coalition of no fewer than 40 Republicans in Congress wrote to Trump urging him not to sign the agreement, expressing disdain for "inappropriate" and "insulting" language that commits the three countries to supporting and protecting sexual orientation and gender identity rights.

Bloomberg via Getty Images Enrique Pena Nieto, Mexico's president, from front left, U.S. President Donald Trump, and Prime Minister Justin Trudeau, sign the United States-Mexico-Canada Agreement (USMCA) on Nov. 30, 2018.