Trump quickly fired back in a tweet, focusing on the former president's language choices: "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!"

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Fox became the latest world leader to raise grave concerns about Trump's approach to global diplomacy, and he said in the interview he does not understand how Hispanic Americans could vote for a presidential candidate like Trump. Fox said he is confident that Trump will not win the presidency.

"Democracy cannot take that, the crazy people that [don't] know what is going on in the world today," said Fox, who then marveled that more than 40 percent of Hispanics who participated in the Nevada caucuses on Tuesday voted for Trump. "I would like to know who those Hispanics are, because ... they are followers of a false prophet. And he’s going to take them to the desert, and if they think that they will benefit with an administration led by Donald Trump, they’re wrong. They must open their eyes. Please: You Hispanics, Latins in U.S., open your eyes. It's not to defend our race, it's 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."

"What is Trump?" Fox said. "He’s not a Republican. Absolutely not. Those are not the Republican principles. He is not a Democrat. He is just himself. He is egocentric."

Fox is not the first prominent Mexican official to criticize Trump. Earlier this month, former Mexican president Felipe Calderon said that his country will not pay for Trump's "stupid wall." Trump responded by saying that such opposition adds another 10 feet to the height of the massive wall — a comment that has become one of Trump's most popular lines at campaign rallies.