White House spokesperson Karoline Leavitt has delivered a blistering attack after a leaked intelligence assessment found America’s strike on Iran did not destroy its nuclear program.

The initial report, prepared by the Defence Intelligence Agency, the Pentagon’s main intelligence arm, found Iran could restart its nuclear program in a matter of months, according to the three sources.

One estimated the restart could be in as little as one to two months.

In response, Leavitt issued an angry statement to CNN, which first reported the assessment, that the “alleged” conclusion was “flat-out wrong”.

“This alleged ‘assessment’ is flat-out wrong and was classified as ‘top secret’ but was still leaked to CNN by an anonymous, low-level loser in the intelligence community,” she said on Wednesday (US time).

“The leaking of this alleged assessment is a clear attempt to demean President [Donald] Trump, and discredit the brave fighter pilots who conducted a perfectly executed mission to obliterate Iran’s nuclear program.

“Everyone knows what happens when you drop 12 30,000-pound (13.6-tonne) bombs perfectly on their targets: Total obliteration,” she added.

The classified assessment is at odds with the statements of Trump and high-ranking US officials – including Defence Secretary Pete Hegseth. They have said last weekend’s strikes, which used a combination of bunker-busting bombs and more conventional weapons, essentially eliminated Iran’s nuclear program.

Trump’s administration told the UN Security Council the US strikes had “degraded” Iran’s nuclear program, short of his earlier assertion that the facilities had been “obliterated.”

A US official who read the assessment noted that it contained a number of caveats and “ifs” and said a more refined report was expected in soon.

Analysts said that, if the assessment was based on satellite imagery, the extent of damage to the deeply buried Fordow uranium enrichment facility would not necessarily be revealed.

Trump has said the attacks were necessary to prevent Iran from developing a nuclear weapon. Iran denies it is seeking such a weapon and says its nuclear program is for peaceful purposes.

Assessing the damage at the Fordow, Isfahan and Natanz nuclear sites is expected to be a difficult task, and the DIA is not the only agency tasked with the job. One source said the assessment was not universally accepted and had generated significant disagreement.

A US official, speaking on condition of anonymity, said the US did not yet know the true extent of the damage.

Still, the initial assessment indicated the strikes may not have been nearly as successful as the Trump administration has claimed.

The sources said the report found that the US attack had caved in facility entrances and destroyed or damaged infrastructure. However, one added, the strike did not collapse underground buildings.

The Washington Post, citing a person familiar the report, said some centrifuges for enriching uranium were intact.

The Pentagon disputed the notion that the damage was insignificant, though it did not dispute that the DIA assessment exists.

“Based on everything we have seen – and I’ve seen it all – our bombing campaign obliterated Iran’s ability to create nuclear weapons,” Hegseth told Reuters.

One source, however, said Iran’s enriched uranium stocks had not been eliminated.

David Albright, a former UN nuclear inspector, said based on post-strike commercial satellite imagery, he believed the US attack effectively destroyed Iran’s uranium enrichment program for now, but failed to eliminate the longer-term threat.

“Iran retains an ability to break out and produce weapon-grade uranium,” said Albright, the head of the Institute for Science and International Security, in a post on X.

He noted that Iran’s stock of near-weapons grade highly enriched uranium – enough for about nine warheads – was unaccounted for, as were advanced centrifuges for an enrichment facility that Iran this month told the IAEA it was preparing.

-with AAP