Move would pave the way for congressional consideration of reworked agreement known as the USMCA

Mr. Trump participates in a ceremonial signing of the U.S.-Mexico-Canada Agreement with outgoing Mexican President Enrique Peña Nieto and Canadian Prime Minister Justin Trudeau.

BUENOS AIRES—President Trump said Saturday he will soon terminate the North American Free Trade Agreement to pave the way for congressional consideration of the reworked agreement known as the USMCA.

Termination would start a six-month withdrawal period and give lawmakers a deadline to choose between the new deal or nothing, the president told reporters aboard Air Force One. His comments came while flying back from Argentina after the Group of 20 summit and a Saturday dinner with Chinese President Xi Jinpingover trade issues.

While here, Mr. Trump participated in a ceremonial signing of the new deal, called the U.S.-Mexico-Canada Agreement, with outgoing Mexican President Enrique Peña Nieto and Canadian Prime Minister Justin Trudeau. At the time, Mr. Trump suggested it wouldn’t face hurdles on Capitol Hill, where ratification is needed.

“That’ll be terminated so Congress will have a choice of the USMCA or pre-Nafta, which worked very well,” Mr. Trump said.

Write to Alex Leary at alex.leary@wsj.com