The North American country won't ever finance such a project, Nieto said in a tweet addressed to President Donald Trump.
Nieto tweet: President @realDonaldTrump: NO. Mexico will NEVER pay for a wall. Not now, not ever. Sincerely, Mexico (all of us).
Speaking at a rally earlier in the day, the U.S. leader had said the neighboring nation would eventually foot the bill for a border wall that he claims will stymie illegal immigration into the U.S.
It's not the first time Nieto has denied the idea.
In 2016, he penned a similar tweet and earlier this year, he postponed plans to visit the White House after an argument with Washington over the matter.