On Wednesday, Fox told CNN that Trump's decision to meet with the Mexican president is an "opportunistic move." He also blasted Trump for lying.
"You cannot cheat people. You have to be straight. You have to speak the truth," Fox said, adding that he hopes Americans will "finally see what is behind Trump, this false prophet that is just cheating everybody."
Fox said he does not understand why the country's president invited Trump to meet with him, but said he hopes he "will take a very firm stand" and call on Trump to apologize to Mexicans.
When asked about Trump's recent comments on immigration and whether the Republican nominee may be softening his position, Fox said that he can't "trust" Trump.
"How can we grant confidence and support to ideas that change every day? He's cynical. He continues to disregard its [sic] own people and disregard Mexicans," he said, adding that Trump cannot win over both "xenophobic" voters and minorities.
Trump responded to Fox Wednesday morning by noting that Fox told Breitbart News in May that Trump should "come to Mexico and to see what Mexico is all about.”
Former President Vicente Fox, who is railing against my visit to Mexico today, also invited me when he apologized for using the "f bomb."
— Donald J. Trump (@realDonaldTrump) August 31, 2016
Fox then hit back in a tweet, telling Trump that he invited Trump to come to the country to apologize.
@realDonaldTrump, I invited you to come and apologize to all Mexicans. Stop lying! Mexico is not yours to play with, show some respect.
— Vicente Fox Quesada (@VicenteFoxQue) August 31, 2016