The first Republican presidential debate isn't until next month, but former Texas governor Rick Perry is already hitting back at fellow GOP contender Donald Trump. In a statement, Perry knocked Trump's criticism of the governor's 14-year tenure in Austin, saying the New York businessman has a "fundamental misunderstanding of border security."

"Make no mistake - border security is a federal responsibility, but when I met with President Obama last year and it became clear he would not act, I told him if he would not secure the border, Texas would," Perry said in his statement, echoing comments he made on MSNBC Thursday morning. "Rather than thanking Texas for stepping into a gap it shouldn’t have to fill, Mr. Trump has made clear that he believes the states should fend for themselves on border security. Not only is this wrong, it perpetuates the same failed policies that have left our southern border porous and vulnerable."

Perry, who has also denounced Trump's characterization of Mexican immigrants, added a word of a caution to Republican primary voters. "I have a message for my fellow Republicans and the independents who will be voting in the primary process: what Mr. Trump is offering is not conservatism, it is Trump-ism – a toxic mix of demagoguery and nonsense," he said.

Trump has been attacking Perry since the first seconds of his presidential campaign and has said the former governor "failed" at the border. Perry, meanwhile, has blasted Trump's plan to build a wall on the southern border as both an impractical and an insufficient way to deal with illegal immigration.