Donald Trump is admonishing Republican rival Ted Cruz to "clean up his act" or run the risk of facing a suit from him charging that he is "not a natural born citizen."

According to CNN, Trump, the GOP front-runner for the party's 2016 presidential nomination, lodged his threat on Friday in a rant on Twitter.

In promoting his own candidacy, Trump has previously argued that if Cruz won the Republican nomination, Democrats would launch a campaign aimed at proving the Canada-born Texas senator was ineligible for the presidency. More recently, the outspoken real estate mogul has openly questioned the sincerity of Cruz's faith, accusing his opponent of being "so dishonest."

In yet another recent Tweet, he again called Cruz's overall level of honesty into question.

Cruz, who won the Iowa caucus and in most national polls is running second overall to Trump, responded by calling Trump's own character into question.

"There is more than a little irony in Donald accusing anyone of being nasty given the amazing torrent of insults and obscenities and vulgarities that come out of his mouth," CNN reports he pointed out during a stop in South Carolina. "Being attacked by Donald, it is always colorful. I will give him this: he's not boring."

Cruz communication director Rick Tyler referred to Trump's onslaught as a "Trumpertantrum," a line the Texas senator has used in recent weeks.

"He needs to go to the time-out chair and think about his choices," added Tyler. That's what you would do with any 3-year old having a Trumpertantrum."

With less than a week remaining before the South Carolina primary, Cruz and Trump are locked in a back and forth battle in the Bible Belt state that could come down to the Evangelical vote.

A recent NBC/WSJ/Marist poll found Trump leading Cruz among that voting bloc 33 to 25 percent. Overall, Trump lead in the state 36 to 20 percent, with Marco Rubio placing third at 14 percent.

Recently, Trump again went on the attack against his chief rival, addressing reports that Cruz had tied him to favoring government-run, universal health care by branding him a total liar.

"I am so against Obamacare," he raged. "I've been saying it for two years in my speeches, I'm going to repeal and replace Obamacare. I don't even know where he gets this."