But the USA negotiators do not want to apply the same guarantees to new Mexican auto plants, the officials said, as the potential threat of 25 percent tariffs would discourage new automotive investment in Mexico to serve the US market.
Trump took a different tact, however, with Canada.
U.S. President Donald Trump said on Friday that the United States and Mexico were making progress on a trade deal, and warned Canada he would tax their auto exports if an agreement can not be reached with Ottawa.
U.S. and Mexican officials have said they aim to conclude discussions this month and it is the third straight week ministers have traveled to Washington for meetings.
But the thornier issues are being left to the end, including the United States demand that NAFTA be approved every five years, a provision known as a sunset clause.
Mexico and Washington have been discussing rules for the automotive sector, which has been a major point of contention between the two countries.
Asked if Canada would rejoin the NAFTA talks next week, Guajardo said, "Hopefully.
"Today more than ever, we see an important window of opportunity, a very significant possibility that (pending issues) will be resolved", said Cervantes, who serves as an industry adviser to the Mexican negotiating team.
Guajardo said that once bilateral U.S.
Mexico's President-elect Andres Manuel Lopez Obrador has vowed that his country would not be threatened by a wall. "We'll keep standing up for Canadian interests as we work toward a modernized trilateral NAFTA agreement".