Story highlights "I've never seen something so incompetently negotiated," Trump said

Trump said Cruz was one of the first to support him when he shared some of his immigration policies

Washington (CNN) Presidential hopefuls Donald Trump and Ted Cruz took to the steps of Capitol Hill on Wednesday, each using their trademark fiery rhetoric to slam President Barack Obama's proposed Iran nuclear deal.

Taking the podium with R.E.M.'s "The End of the World" blaring, the real estate mogul used a brief speech to say that if elected, four Americans being held in Iran will return to the U.S. before he takes office.

"I've never seen something so incompetently negotiated -- and I mean never," Trump said.

Trump followed Cruz, who said that if Congress approves the current deal, Iran could end up developing a weapon that could kill millions along the Atlantic seaboard.

"If Senate Democrats decide that party loyalty matters more than national security and if Republican leadership decides that showboating is more important than stopping this deal, then the single most important issue in 2016 will be stopping Iran from acquiring a nuclear weapon," he said.

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