Influential U.S. lawmakers who could have the final say on the fate of NAFTA were travelling to Montreal Friday to get an update on negotiations.

Ten members of the Congressional ways and means subcommittee on trade were expected to arrive Friday night, with a series of meetings to follow over the next two days.

The visit will include a closed-door conversation with Andrew Leslie, Canada's parliamentary secretary of foreign affairs.

Leslie is expected to use the face time to repeat once again Canada's message about the importance of the trilateral trade deal, a source with direct knowledge of the trip told CBC News.

The U.S. members are believed to be a mix of pro-trade Republicans as well as Democrats.

Prime Minister Justin Trudeau met with members of this same committee last fall during a trip to Washington, where his message of continued economic co-operation was mostly well received.

This is the first time this group has traveled to the site of NAFTA talks.

Prime Minister Justin Trudeau takes part in a meeting with the House ways and means committee on Capitol Hill in Washington in October. (Sean Kilpatrick/Canadian Press)

The lawmakers are considered critical players in the trade talks, since a U.S. withdrawal from NAFTA requires congressional approval.

Even if Donald Trump triggers the withdrawal process, these are some of the members of Congress who could stop the process with their votes.

"Members of Congress travel to hot spots in the world, and that doesn't often include Canada," said Scotty Greenwood, a former U.S. diplomat.

"Canada is a hot spot economically right now, and I think it's positive," she told reporters in Montreal.

More rounds of talks likely

The lawmakers arrive on the fourth day of NAFTA talks, where new signs of progress are emerging.

The Americans have still not rejected any of Canada's new proposals on the key sticking points at the negotiating table, and talks are being described as constructive.

There is even new speculation, about additional rounds of NAFTA talks. If extra discussions are added, it would be considered a sign that negotiators see enough progress that there is value in keeping the conversation going.

Canada's chief negotiator wouldn't comment on the speculation, but Quebec's chief negotiator did offer some insight.

"We agreed there's going to be a round in Mexico, there's probably going to be a round in Washington in April, something like that, and probably going back to Canada in May," Raymond Bachand told reporters.

But he was very clear to offer some caution: "It's as uncertain as the rest."