Update Feb. 25, 2016 at 4:30 p.m. Donald Trump took to Twitter to demand an apology from former Mexican President Vicente Fox:

FMR PRES of Mexico, Vicente Fox horribly used the F word when discussing the wall. He must apologize! If I did that there would be a uproar! — Donald J. Trump (@realDonaldTrump) February 25, 2016

In an exclusive interview earlier this week with Univision and Fusion anchor Jorge Ramos, former Mexican President Vicente Fox said he’s troubled by the show of support the Republican presidential frontrunner received at the Nevada caucus.

Fox, in an interview for Univision’s Al Punto set to air this Sunday, questioned the claim that Trump won over 44% of Hispanics in that caucus. “I’d like to know who those Hispanics are,” he said speculating many could be falling for “a false prophet.”

Slamming Trump’s anti-immigration rhetoric and his campaign promise of building a wall at the U.S.-Mexico border, Fox urged Hispanics to “open their eyes.”

“Please, you Hispanics, Latinos in the U.S., open your eyes. It’s not to defend our race. Not to defend our creed. It’s to defend this very same nation that is hosting you. This nation is going to fail if it goes into the hands of a crazy guy,” warned the former Mexican commander-in-chief.

Fox also assured Ramos, in much more colorful language, there’s no way Mexico is going to pay for Trump’s wall.

Fox is not the only former Mexican president who has come out to publicly denounce Trump’s wall proposal. Former President Felipe Calderón recently told CNBC there’s no way Mexicans are going to pay for a “stupid wall.”

Watch the full interview below: