National Security Adviser H.R. McMaster said Thursday that the effects of the Iran Nuclear Deal have been the opposite of what was intended, allowing Iran to continue missile development.

McMaster spoke to CNN’s Chris Cuomo, castigating the deal’s sunset clause, which lifts restrictions on Iran’s nuclear program after 2025, as well as the trustworthiness of the Iranian regime. He said the deal is "fundamentally flawed," and quoted President Donald Trump’s declaration that the deal, agreed upon by his predecessor Barack Obama, was the worst of "all-time."

"The deal is fundamentally flawed," McMaster said. "As the president said, he called it the worst deal of all-time. It gave the Iranian regime all the benefits up front."

"The flaws of the deal, the sunset clause that could really give this regime, who is not trustworthy, obviously, cover to advance a nuclear program and then have this threshold capability," he added.

Cuomo argued that the deal has made some difference, and by some accounts, at least slowed the development of weapons in Iran. He inquired whether the Iran deal was simply the best deal possible because it is what Obama agreed to after negotiations, but McMaster disagreed.

McMaster said the Iranian regime has crossed the line by spinning unauthorized centrifuges, and corrective action must be tougher.

"Iran is continuing missile development, missile development that could be paired with a nuclear program later," McMaster said. "The regime has not just walked up to the line but crossed the line, spinning too many centrifuges, too much heavy water."

"So while the IAEA [International Atomic Energy Agency], the monitoring body, called them out on it and they’ve corrected some of this: How do you trust this regime to do it?" he asked.

He stated the need for more rigorous enforcement, and called the sunset clause the deal’s "fundamental flaw."

"Much more rigorous enforcement is needed – the need to address the fundamental flaw, the sunset clause, the need to address other capabilities that could then threaten the world, from this autocratic, theocratic regime in Iran," McMaster said.

He also described the wider range of Iran’s negative influence, calling for an overall strategy to prevent them from destabilizing the Middle East.

"So, these are the things we have to work on together, but in the context of an overall Iran strategy, because Iran is destabilizing not just the Middle East, but poses a broader threat," McMaster said. "Iran is perpetuating this humanitarian and political crisis in the Middle East."