Former Republican presidential nominee Mitt Romney slammed Texas Sen. Ted Cruz over his criticism of the U.S.-Iran nuclear deal.

Earlier this month, the U.S. and five other world powers reached a historic agreement with Iran that places limits on its nuclear program for the next 10 years. In exchange, the world powers agreed to ease economic sanctions on the Islamic republic. As a result, Iran will be granted access to billions of dollars in relief and allowed to sell oil to many once again.

Following Obama's announcement about the deal, many Republicans argued that Iran would use some of the newfound wealth to fund terrorism once international sanctions are lifted.

Cruz, however, warned that the Obama administration will "become the leading financier of terrorism against America in the world," during a July 15 Fox News interview.

He added, "I've heard this referred to before as the 'Jihadist Stimulus Bill.'"

He also said on Monday that if the deal goes into effect, the Obama administration will become "the world's leading financier of radical Islamic terrorism," reports CNN.

Although Romney admitted that he, too, is not fond of the deal, he said that Cruz's accusations that Obama will become a sponsor of Islamic extremist were out of line.

"I am opposed to the Iran deal, but @SenTedCruz is way over the line on the Obama terrorism charge. Hurts the cause," Romney tweeted on Thursday.

Cruz fired back at the former Massachusetts governor on Thursday afternoon during an appearance on the Chad Hasty radio show.

"When you send billions of dollars to Jihadists trying to kill Americans, you bear responsibility for the murder that they carry out with the money you have given them," said the 2016 hopeful. "And you know one of the reasons why Republicans keep getting clobbered, we have leader like Mitt Romney and like Jeb Bush who are afraid to say that."

Cruz went on to ridicule Romney, saying, "So Mitt Romney's tweet today said, 'Gosh, this rhetoric is not helpful.' John Adams famously said, 'Facts are stubborn things.' Describing the actual facts is not using rhetoric; it is called speaking the truth," said Cruz, according to Business Insider.