Key Points

Grossi's comments appear to support an early assessment from the Pentagon's Defense Intelligence Agency, which suggests the United States' strikes on key Iranian nuclear sites last week did not destroy the core components of its nuclear programme, and likely only set it back by months.

While the final military and intelligence assessment has yet to come, Trump has repeatedly claimed to have "completely and totally obliterated" Tehran's nuclear programme.

The 12-day conflict between Israel and Iran began earlier this month when Israel launched an unprecedented attack it said aimed at preventing Tehran from developing a nuclear bomb. Iran has insisted its nuclear programme is for peaceful purposes.

The US then struck three key Iranian nuclear sites before a ceasefire began. The extent of the damage to Tehran's nuclear programme has been hotly debated ever since.

US military officials have in recent days provided some new information about the planning of the strikes, but offered no new evidence of their effectiveness against Iran's nuclear programme.

Following classified briefings this week, Republican lawmakers acknowledged the US strikes may not have eliminated all of Iran's nuclear materials - but argued that this was never part of the military's mission, CNN reported.

Meanwhile, The Washington Post reported on Sunday that the US had obtained intercepted messages in which senior Iranian officials discussing the attacks said they were not as destructive as they anticipated.

Asked about the different assessments, Grossi, Director General of IAEA, said, "This hourglass approach in weapons of mass destruction is not a good idea."

"The capacities they have are there. They can have, you know, in a matter of months, I would say, a few cascades of centrifuges spinning and producing enriched uranium, or less than that. But as I said, frankly speaking, one cannot claim that everything has disappeared and there is nothing there," CNN reported, quoting Grossi.

"It is clear that there has been severe damage, but it's not total damage," Grossi went on to say. "Iran has the capacities there; industrial and technological capacities. So if they so wish, they will be able to start doing this again."

CNN further reported that Grossi said the IAEA has resisted pressure to say whether Iran has nuclear weapons or was close to having weapons before the strikes.

- ANI