Vienna: Any collapse of the 2015 nuclear deal between Iran and major powers would be a "great loss", the head of the UN atomic agency policing the accord said on Monday, alluding to a US threat to pull out of it.
President Donald Trump has threatened to withdraw the United States from the accord unless Congress and European allies help "fix" it with a follow-up agreement.
International Atomic Energy Agency chief Yukiya Amano, whose agency is verifying Iranian compliance with restrictions on its disputed uranium enrichment work imposed by the deal, has long called the pact a "net gain" for nuclear verification, since it has provided the IAEA with more thorough oversight of Iran.
But in a speech on Monday to a quarterly meeting of the IAEA's Board of Governors, he went further, evoking the possibility of the deal, officially known as the Joint Comprehensive Plan of Action (JCPOA), unravelling.
"The JCPOA represents a significant gain for verification," Amano said, according to a text of his speech published by his agency. "If the JCPOA were to fail, it would be a great loss for nuclear verification and for multilateralism."
Amano said Iran was implementing its commitments under the deal, which also lifted painful economic sanctions against the Islamic Republic. He confirmed the findings of a quarterly, confidential IAEA report on Iran issued last month.
But in remarks that might concern Western powers, Iran asserted on Monday it could produce higher enriched uranium within two days if the United States bolted from the accord, according to state-run Arabic language al-Alam TV.
"If America pulls out of the deal ... Iran could resume its 20 per cent uranium enrichment in less than 48 hours," Behrouz Kamalvandi, spokesman for the Atomic Energy Organisation of Iran, told al-Alam TV.
Uranium refined to 20 per cent fissile purity is beyond the 5 per cent normally required to fuel civilian nuclear power plants, though still short of the highly enriched, or 80-90 per cent, purity needed for the core of a nuclear bomb. Kamalvandi, reiterating Tehran's official stance, said the nuclear deal is not re-negotiable.
The deal's European signatories - Germany, Britain and France - as well as Russia and China are committed to preserving the agreement, deeming it crucial to reducing the risk of wider international conflict.
As mentioned by the confidential IAEA report, Amano also said the agency had requested clarification from Iran about its plans for nuclear-powered naval vessels, suggesting the IAEA has still not heard back from the Islamic Republic.
"The agency has requested Iran to provide further clarifications regarding its plans relevant to the development of the nuclear fuel cycle related to naval nuclear propulsion," Amano told the closed-door meeting of 35 member states.
Iran has long said publicly that it intends to develop nuclear propulsion for naval vessels, though analysts and diplomats say this remains a distant prospect. It formally notified the IAEA of that intention in January in what was widely seen as a diplomatic warning shot aimed at Trump's administration, which reversed a policy of detente with Iran introduced by his predecessor Barack Obama.
But the move prompted the IAEA to ask what exactly Iran's plans are. France's foreign minister visited Iran on Monday on a delicate mission to affirm European support for the nuclear deal that eased the isolation of Iran's oil-based economy, while echoing US concern about Tehran's ballistic missile tests and role in Middle East conflicts such as Syria.