US President Donald Trump said Saturday he will soon notify Congress that he plans to end the NAFTA agreement with Mexico and Canada in favor of a new regional trade deal, setting up a potential clash on Capitol Hill.

President Donald Trump, center, sits between Canada's Prime Minister Justin Trudeau, right, and Mexico's President Enrique Pena Nieto as they sign a new United States-Mexico-Canada Agreement that is replacing the NAFTA trade deal, during a ceremony at a hotel before the start of the G20 summit in Buenos Aires, Argentina, Friday, Nov. 30, 2018. (Photo: AP)

Trump, traveling home from a G20 summit in Argentina, told reporters aboard Air Force One that he would give formal notice to Congress on "terminating" NAFTA "within a relatively short period of time."

That would trigger a six-month waiting period before the US could leave the pact -- during that time, US lawmakers would be asked to approve the new deal signed on Friday with America's neighbors.

Trump says the new pact -- known in Washington as the US-Mexico-Canada Agreement (USMCA) -- will help US workers, especially in the auto industry, and better safeguard intellectual property.

"We get rid of NAFTA. It's been a disaster for the United States," said Trump, who insisted that the North American Free Trade Agreement, in place for nearly a quarter-century, was a killer of American jobs.

"That'll be terminated so Congress will have a choice of the USMCA or pre-NAFTA, which worked very well," the Republican president said.

The signing of USMCA was a victory for Trump, following months of tense and difficult negotiations with Ottawa and Mexico City.

Trump said Friday that he did not foresee a problem with getting congressional approval, but some Democrats -- who will control the US House of Representatives as of January -- have expressed skepticism.

Nancy Pelosi, the frontrunner to regain her position as Speaker of the House, on Friday called the deal a "work in progress."

"What isn't in it yet are enough enforcement reassurances regarding workers" and the environment, she told a press conference.

"This is not something that we have a piece of paper where we can say yes or no to it," said Pelosi, who added that Mexico had not yet passed a law on wages and working conditions.

The new deal also requires legislative approval in Canada and Mexico.