The modernization of the 1994 North American Free Trade Agreement (NAFTA) has seen "very important developments," though much remains to be done, Mexican Economy Minister Ildefonso Guajardo said on Monday.

NAFTA partners Mexico, Canada and the United States are still at odds over many issues, Guajardo, who heads Mexico's negotiating team, told reporters on the sidelines of an academic event.

One of those issues is a proposal by the United States to tighten the rules of origin in the automobile sector, a move both Canada and Mexico have opposed.

However, Mexico has made a counter proposal and the U.S. has modified its original demands, so negotiators meeting in Washington over the past two weeks have been looking at both of those proposals, said Guajardo.

"In two weeks there have been very important developments in balancing out several topics of interest on the table in regard to Mexico and the United States, from a trade perspective," Guajardo said.

"The thing is that there are many topics on the table," said Guajardo, who added he plans to travel to Washington this week to check on the progress of the talks.

"There are automotive rules of origin, there are rules in the fiber optics sector, there are rules in steel, and we are reviewing the whole package of regulations," said Guajardo.

NAFTA was subjected to renegotiation in August 2017 on the urging of U.S. President Donald Trump, who believes the original trade agreement harms U.S. industry and jobs.

Guajardo was at Mexico's prestigious Colegio de Mexico to inaugurate a new postgraduate degree in international trade negotiation.