– The U.S. and Mexico are close to resolving their differences on the North American Free Trade Agreement and may wrap up as soon as Monday, said three people familiar with the progress, clearing the way for Canada to possibly return to talks to update the three-nation trade deal.

The nations achieved significant breakthroughs in the past several days on the issues of automobiles and energy, according to the sources, who spoke on the condition of anonymity. Talks were expected to continue Sunday.

President Donald Trump was optimistic Saturday, writing on Twitter that the U.S. could have a “big Trade Agreement” with its southern neighbor soon. The terms of any deal struck by U.S. Trade Representative Robert Lighthizer would need Trump’s approval.

It remains unclear how U.S. and Mexican negotiators would make public the completion of work on their issues, given that Mexican Economy Minister Ildefonso Guajardo has signaled that the nation won’t make an announcement on NAFTA until Canada also signs on to a new deal.

White House press secretary Sarah Huckabee Sanders said Sunday that the administration has “no announcements or anything finalized at this time.”

The administrations of Trump and Enrique Peña Nieto have been working for five weeks to resolve their issues so Canada can rejoin the talks to update the decades-old agreement. The U.S. and Mexico are pushing for an agreement this month that would give the countries time to sign it before Mexico’s President-elect Andres Manuel López Obrador takes office in December.

The U.S. and Mexico had largely focused on the thorny issue of car manufacturing, as the Trump administration pushes for a deal that would boost factory jobs in America. The U.S. has proposed tightening regional content requirements for car production and having a certain percentage of a car manufactured by higher-paid workers.

While a U.S. proposal to increase tariffs on cars imported from Mexico that don’t meet stricter new content rules was a sticking point as recently as last week, that issue appeared to be resolved by Thursday.