Former Mexican President Vicente Fox is making his position clear on Donald Trump’s pledge to make Mexico pay for a wall along the U.S.-Mexico border. “I’m not going to pay for that f***ing wall. He should pay for it,” Fox told Fusion’s Jorge Ramos in an interview published Thursday. Trump quickly responded on Twitter. “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!” he tweeted. Fox, who was president from 2000-2006, also pushed back on Trump’s claim that he was winning support among Latinos, after entrance polls at Tuesday’s Nevada caucuses showed him winning Latino Republican caucusgoers. “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,” Fox told Fusion. What Nevada showed about Trump’s Hispanic support - and what it didn’t Trump has often insisted that he will build a wall along the border and convince Mexico to pay for it. The promise is a staple of his campaign and has often been turned into a call-and-response at his rallies, where he asks supporters who will pay for the wall and they yell back, “Mexico!” Pope Francis said last week that Trump “is not Christian” if he seeks to build a wall and deport undocumented immigrants.