MEXICO CITY, May 15 (Xinhua) -- Negotiations to modernize the North American Free Trade Agreement (NAFTA) are unlikely to reach an accord in principle by May 17, Mexican Economy Minister Ildefonso Guajardo said Tuesday.

The three NAFTA partners, Mexico, Canada and the United States, continue to disagree on several issues, he said.

"The possibility that by Thursday we will have all of the negotiation (wrapped up) is not likely. We don't think it will happen by Thursday," Guajardo said during an interview at a morning television news program.

May 17 loomed as a deadline for a preliminary agreement after Paul Ryan, the speaker of the U.S. House of Representatives, last week said that for Congress to approve a revamped NAFTA, an agreement in principle had to be submitted by then.

Otherwise, Congress would not have enough time to debate and approve a new deal before legislative elections in November.

"The conditions are still not there at this time," affirmed Guajardo, who heads Mexico's negotiating team.

Among the issues the three sides have yet to agree on is a U.S. proposal to include a so-called sunset clause that would allow the deal to automatically expire every five years, pending renewal. Neither Canada nor Mexico wants that.

However, the trio may be closer to agreeing on automotive rules of origin that place caps on the amount of foreign-made parts allowed in vehicles manufactured in North America, said Guajardo.

Washington wants less foreign-made parts and more U.S.-made components, while Canada and Mexico want to preserve the existing limits.

"We could see the elements to arrive at a balanced agreement. The problem is that you have a series of additional elements that are changing the nature of what a trade agreement is. That's where we are seeking solutions that will lend certainty to what we are negotiating," he said.

"You have to continue to negotiate and the moment you reach a good negotiation, close the deal," he added.

Guajardo proposed another possible end date, saying NAFTA talks could conclude by Mexico's presidential elections on July 1 or shortly after.

The negotiations began in August, after U.S. President Donald Trump took office. Trump campaigned on a platform to strengthen U.S. industry and employment, in part by renegotiating the 1994 trade agreement.