Newt Gingrich on Sunday warned that a contested convention to try to preventfrom securing the GOP nomination would have a disastrous effect on the Republican party.

"If Trump comes in [to the convention] with 45 percent or more of the delegates, he's gonna be the nominee," the former House Speaker said in a radio interview with John Catsimatidis. "You would have a civil war if people stepped in, if the old guard stepped in, and tried to steal the nomination."

Gingrich added that if the real estate mogul loses in some key states then his rivals could make the case for taking the race to convention floor.

"Now if Trump somehow stumbles in Florida, stumbles in Ohio, you've got a little bit of a different story – now there's a real brawl."

Still, Gingrich says that if Trump takes those key states then the establishment should not try to attempt block him from the nomination.

"And frankly, if he wins both Ohio and Florida it's over," he added.