Republican presidential frontrunner Donald Trump warned that the Iran nuclear deal that is being trumpeted by the Obama administration could lead to a "nuclear holocaust."

On NBC's "Meet The Press" Sunday, Trump said as a businessman, he has taken over bad contracts and turned them into good ones—just like what he intends to do with the Iran nuclear accord. If elected president, he said he would not scrap the agreement as some of his fellow candidates want to do on their first day in office. Instead, he said he "would police that contract so tough that they don't have a chance," according to Newsmax.

Trump lambasted State Secretary John Kerry for negotiating a "bad deal" with Iran. "The people that negotiated that deal, mainly Kerry and his friends, are incompetent," he said.

He said if the contract was negotiated under his administration, he would never have allowed Iran to get back its $150 billion worth of frozen assets, which it will get under the present deal. He would have also pressed for the release of the four Americans being held in Iran as a condition for the talks.

Trump said he expects Iran to use the huge amount of money it will get to acquire nuclear weapons.

"I would have told them [Iranians] up front, you will never get your $150 billion back. They are going to be such a wealthy, such a powerful nation, they're going to have nuclear weapons. They are going to take over parts of the world you wouldn't believe. And I think it's going to lead to nuclear holocaust," he said.

Trump continued to lead the Republican presidential race, which also saw a major shakeup among the other top contenders.

The latest Fox News poll showed Trump getting 25 percent among likely Republican primary voters, slightly down by 1 percentage point from the same poll conducted last July 30 to Aug. 2.

Retired neurosurgeon Ben Carson has taken over second place with 12 percent, up by 5 percentage points, while Texas Sen. Ted Cruz is now at third place with 10 percent, up by 4 percentage points.

Jeb Bush drops to fourth with 9 percent followed by Mike Huckabee and Scott Walker with 6 percent each, Carly Fiorina with 5 percent, John Kasich and Marco Rubio with 4 percent, and Rand Paul and Chris Christie with 3 percent.

The poll was conducted from Aug. 11-13 among 1,008 registered voters.