Donald Trump and Mexico's Former President Vicente Fox Spar on Twitter Before Visit

— -- Donald Trump and Mexico’s former President Vicente Fox are engaged in a bitter back-and-forth just hours before the Republican presidential nominee is scheduled to visit the country.

It all started during an interview with CNN this morning, when Fox called Trump a “false prophet” while deriding his planned meeting with Mexico's current President Enrique Peña Nieto.

"Trump is using Mexico, is using President Peña to push his sinking poll numbers," Fox said on CNN's "New Day." “So it's a very opportunistic move and I hope U.S. public opinion, U.S. citizens can see this and finally, and finally see what is behind Trump, this false prophet that is just cheating everybody.”

After Fox’s interview this morning, Trump took to Twitter to fire back at Fox.

Fox was quick to respond, telling Trump to “stop lying” and “show some respect.”

Fox has repeatedly decried Trump’s campaign on social media. And in a Feb. 25 interview with Jorge Ramos on Fusion, the former Mexican president responded to the real estate mogul’s plan to build a wall between Mexico and the United States.

“I’m not going to pay for that f---ing wall! He should pay for it. He’s got the money,” Fox said. “What is Trump? He’s not a Republican. Absolutely not. Those are not the Republican principles. He’s not a Democrat. He is just himself. He is egocentric.”