Former New York City Mayor Rudy Giuliani believes that Donald Trump could cancel the nuclear deal with Iran on his first day as president since he’s not bound by it.

Giuliani, who is said to be one of Trump’s top candidates for Secretary of State along with former UN Ambassador John Bolton, told the Wall Street Journal’s Gerry Baker that Trump could take this action because President Barack Obama never submitted the Iran deal to the Senate for approval.

"First of all, the president has a lot of options. President Obama didn't do what he should have done, under the Constitution. He should have submitted that to the Congress, that's a treaty. There's no way of escaping the fact that that's a treaty," argued Giuliani.

"It should have been submitted to the Senate... he never did. What that means is, that deal is over with the current president. Trump can disavow it, as a matter of law, like that," he continued.

Trump has continuously spoken out against the nuclear deal with Iran, saying during the presidential campaign that the deal was “disastrous” and one of the worst agreements ever negotiated.

Last Wednesday, a day after Trump was elected, Iran's President Hassan Rouhani said there was "no possibility" that the nuclear deal with world powers would be overturned by the President-elect.

Other Iranian officials, like Rouhani, have downplayed Trump’s threats to annul the nuclear deal, insisting he cannot do so even if he wishes.

One of Trump's foreign policy advisers, Walid Phares, said last week that while Trump might not actually rip up the agreement, he would act to change it.