A classified preliminary US intelligence report has concluded that American strikes on Iran set back Tehran's nuclear program by just a few months — rather than destroying it as claimed by President Donald Trump.

US media on Tuesday cited people familiar with the Defense Intelligence Agency findings as saying the weekend strikes did not fully eliminate Iran's centrifuges or stockpile of enriched uranium.

The strikes sealed off entrances to some facilities without destroying underground buildings, according to the report.

White House Press Secretary Karline Leavitt confirmed the authenticity of the assessment but said it was "flat-out wrong and was classified as 'top secret' but was still leaked."

"The leaking of this alleged assessment is a clear attempt to demean President Trump, and discredit the brave fighter pilots who conducted a perfectly executed mission to obliterate Iran’s nuclear program," Leavitt posted on X.

"Everyone knows what happens when you drop fourteen 30,000 pound bombs perfectly on their targets: total obliteration," she added.

US B-2 bombers hit two Iranian nuclear sites with massive GBU-57 bunker-buster bombs over the weekend, while a guided missile submarine struck a third with Tomahawk cruise missiles.

Trump called the strikes a "spectacular military success" and said they had "obliterated" the nuclear sites, while Defense Secretary Pete Hegseth said Washington's forces had "devastated the Iranian nuclear program."

General Dan Caine, the top US military officer, has struck a more cautious tone, saying the strikes caused "extremely severe damage" to the Iranian facilities.

Iran's government said Tuesday that it had "taken the necessary measures" to ensure the continuation of its nuclear program.

"Plans for restarting (the facilities) have been prepared in advance, and our strategy is to ensure that production and services are not disrupted," the head of the Atomic Energy Organization of Iran, Mohammad Eslami, said in a statement aired on state television.

An adviser to Iran's supreme leader, Ayatollah Ali Khamenei, meanwhile said his country still had stocks of enriched uranium and that "the game is not over."

Israel launched an unprecedented air campaign targeting Iranian nuclear sites, scientists and top military brass on 13 June in a bid to set back Tehran's nuclear efforts.

Trump had spent weeks pursuing a diplomatic path to replace the nuclear deal with Tehran that he tore up during his first term in 2018, but he ultimately decided to take military action.

The US operation was massive, with Caine saying it involved more than 125 US aircraft including stealth bombers, fighters, aerial refueling tankers, a guided missile submarine and intelligence, surveillance and reconnaissance aircraft.