"Frankly, that deal is an embarrassment to the United States, and I don't think you've heard the last of it — believe me," Trump said.
Trump called Iran's government a "corrupt dictatorship" and accused the state of supporting terrorism.
He added, "We cannot let a murderous regime continue these destabilizing activities while building dangerous missiles, and we cannot abide by an agreement if it provides cover for the eventual construction of a nuclear program."
Trump's long been critical of the nuclear deal. But thus far in his presidency, he's stuck by it and recertified the agreement twice. The next deadline for that is Oct. 15.
Essentially, at the deadline the president will say whether Iran has kept its end of the bargain. If the president says it has, the U.S. will continue to waive nuclear-related sanctions against Iran.
If Trump decides not to recertify, Congress then has 60 days to decide if it will reimpose the sanctions against Iran that are currently lifted under the deal.
Even if Trump keeps the agreement going in October, the issue isn't over. Under U.S. law, the president has to recertify the deal every 90 days.