Hours before the GOP presidential candidates take to the debate stage tonight in Las Vegas, where border security and immigration are expected to be hot-button issues, former Mexican president Vicente Fox scolded two of them for their “stupid” and “confusing” plans to close the porous border.

“This guy who wants to put electric wire on top of the fence at 20 meters high so the migrants die,” Fox said, referring to Herman Cain’s proposal to build an electric border fence, “is incredible, it’s nonsense.”

Fox said the United States might as “put water with crocodiles” along the border.

Cain tried to play off the comments he made Saturday that the border fence should be “twenty feet high, with barbed wire, electrified. With a sign on the other side that says it can kill you,” by saying Monday that they were just a “joke.”

But at the same news conference, the former Godfather’s Pizza CEO suggested that he did, in fact, support an electric fence.

“I don’t apologize for using a combination of a fence and it might be electrified,” Cain said. “I’m not walking away from that. I just don’t want to offend anybody.”

Cain was not the only Republican White House hopeful to spark the former Mexican president’s ire. Fox also blasted Texas Gov. Rick Perry for suggesting that the U.S. military should engage in “security operations” in Mexico.

“I would die to prevent that,” Fox said today after speaking to the libertarian Cato Institute in Washington, D.C. “No more wars, no more U.S. army in our territory.”

Perry said earlier this month that  “it may require our military in Mexico” to fight the Mexican drug cartels.

“Make no mistake about it, what we are seeing south of our border is nothing short of a war being waged by these narcoterrorists,” Perry said in a speech at the socially conservative Values Voter Summit. ”To face this threat, we shouldn’t take any options off the table, including security operations in cooperation with the Mexican government as we did with Colombia some years ago.”

In his speech today, Fox pushed back against calling Mexican drug violence a “war,” saying that terminology is “taking us nowhere.” He said  Perry’s stance on border security is “confusing” because he supports allowing illegal immigrants to pay in-state tuition at Texas public universities, but then takes a militaristic tone toward securing the border.

“I don’t see a clear position,” Fox said. “On one side I hear him with a very great compassion and understanding of the human side of migrants here. He’s willing to open up opportunities for them. On the other hand he’s talking about a very strong enforcement in the border, so I don’t think it’s clear.”

Fox publicly praised the Texas governor after he signed the 2001 tuition law for “having taken that step forward” to give Mexican migrants access to Texas universities.

Perry’s fellow GOP candidate Mitt Romney seized on Fox’s comments in a campaign ad released last month attacking Perry for his support of the tuition law. A full 25 seconds of the minute-long ad is a clip of Fox congratulating Perry on the law’s passage.

ABC News’ Sarah Parnass contributed to this report.