Canada and Mexico will formally oppose some of the Trump administration’s proposed revisions to the North American Free Trade Agreement Tuesday, but will not walk out on the talks, according to sources close to the negotiations.

Still, the governments’ rejection heightens the possibility that President Trump will formally pull the U.S. out of the 1993 trade deal, a threat he has made repeatedly in the past. Trump has said changes that benefit the U.S. economy must be made or the U.S. might leave the deal.