Iranian President Hassan Rouhani has defended a landmark nuclear deal with Western powers and said that US President Donald Trump could not undermine it.

Under the 2015 agreement, Tehran agreed to limit its disputed nuclear programme in return for the easing of economic sanctions.

Trump has repeatedly criticised the accord, which was negotiated by the Obama administration and enshrined under United Nations Security Council Resolution 2231, as "the worst deal ever" and "an "embarrassment".

He has to review it by October 15 and decide if Iran is keeping to its end of the bargain, and whether it serves US interests.

On Thursday, he said Iran had not lived up to the spirit of the deal, and reports have suggested he may decertify it - a step that potentially could cause the agreement to unravel.

READ MORE: Donald Trump denounces Iran over nuclear deal

Speaking on Saturday at a ceremony at Tehran University marking the start of the university academic year, Rouhani said the deal's "issues and benefits" are"not reversible".

"No one can turn that back, not Mr Trump or anyone else," he said, according to state media.

"Even if 10 other Trumps are created in the world, these are not reversible."

'Why did you trust America?'

The prospect of Washington reneging on the deal has worried some of the US allies that helped negotiate it, especially as the world grapples with another nuclear crisis - North Korea's nuclear and ballistic missile development.

If Trump does not certify that Iran is in compliance, the US Congress will have 60 days to decide whether to reimpose sanctions waived under the deal. United Nations inspectors have verified Iranian compliance with the terms.

Rouhani said on Saturday that if the US violated the deal then it would hurt its own reputation in the international community.

"If America carries out any violations today, the whole world will condemn America. They will not condemn Iran," Rouhani said, according to state media. "Then they will say, 'Why did you trust America and sign an agreement with them?'"

READ MORE: Iran's Zarif slams US 'addiction' to sanctions

In separate comments to Al Jazeera, Iranian Foreign Minister Javad Zarif also condemned Trump over his threats to walk away from the deal, saying that the US leader's remarks would not "help peace and security in the region" and would harm the long-term interests of the United States.

"I think it is an ill-informed statement, because certainly, any deal would not be a perfect deal for all sides; it has to be less than perfect so all sides can live with it," said Zarif, warning that the international community could never trust the US again if it violated the deal.

Zarif said any breaches of the deal by the US would result in Iran's partial or complete withdrawal from the agreement, noting that Tehran would be undeterred by threats of sanctions.

"The nuclear deal is the result of 10 years of posturing and two years of negotiations. Unfortunately, this administration is going back to posturing," he said. "They [US leaders] have immunised us to US sanctions. From a global perspective, it would seem the United States is addicted to sanctions."