Former Mexican President Vicente Fox got explicit live on CNN Friday morning as he slammed President TrumpDonald John TrumpHouse Democrat slams Donald Trump Jr. for ‘serious case of amnesia’ after testimony Skier Lindsey Vonn: I don’t want to represent Trump at Olympics Poll: 4 in 10 Republicans think senior Trump advisers had improper dealings with Russia MORE's vow to make Mexico pay for a wall along the United States' southern border.

"You can use my words. We will never pay for that f------ wall," he told a stunned CNN host Alisyn Camerota on "New Day."

"Who can think about a country paying for a wall that is going to be built in the neighbor's territory? Or why should Mexico pay for a wall? What's the reason?" he continued. "We don't need a wall."

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It's not the first time Fox has used such language on live television to describe Trump's proposed border wall. In an interview with Fox Business Network last year, the former Mexican leader also said that his country would not pay for "that f------ wall."

Fox also used the same line in an interview with Fusion's Jorge Ramos, though that interview was not aired live.

Fox, who served as Mexico's president from 2000 to 2006, has been among the most vocal critics of Trump's border wall.

Fox's comments on CNN came a day after The Washington Post published a leaked transcript of Trump's first call with current Mexican President Enrique Peña Nieto.

In the call, Trump urged the Mexican leader to stop publicly saying that his country will not pay for the project.

"We cannot say that anymore because if you are going to say that Mexico is not going to pay for the wall, then I do not want to meet with you guys anymore because I cannot live with that," Trump said.

Trump also called the border wall "the least important thing" the two leaders discussed but that it had political importance for him.

"Believe it or not, this is the least important thing that we are talking about, but politically this might be the most important," Trump said according to the transcript. "But in terms of dollars — or pesos — it is the least important thing."