Trump, Trudeau differ on NAFTA talks

US President Donald Trump has suggested the US, Mexico and Canada might not come to an agreement on the renegotiation of a more than 20-year-old North American trade deal as he held talks with Canadian Prime Minister Justin Trudeau at the White House.

Trudeau however said after the meeting that he remained optimistic about the prospects of the North American Free Trade Agreement (NAFTA) as the fourth round of talks got underway outside Washington.

Trump, who has long criticised the agreement and nearly withdrew from the pact earlier this year before instead pursuing renegotiation, said, "It's possible we won't be able to make a deal and it's possible that we will."

His primary goal was to protect US workers, Trump said, noting Trudeau would also seek to protect Canadians.

"I think Justin understands that if we can't make a deal, it will be terminated and that will be fine," he said. "They're going to do well. We're going to do well. But maybe that won't be necessary. But it has to be fair to both countries."

Canada remains focused on the renegotiation, Trudeau said, while acknowledging the penchant of the US leader to make surprising decisions. Trudeau was to travel to Mexico City after his trip to Washington to hold talks with Mexican President Enrique Pena Nieto.