US Secretary of Defense Pete Hegseth has said that he is unaware of any intelligence suggesting Iran had moved any of its highly enriched uranium to shield it from American strikes over the weekend.
US military bombers targeted three nuclear facilities, using more than a dozen bunker-buster bombs.
The results of the strikes are being closely watched to see how far they may have set back Iran's nuclear programme.
"I'm not aware of any intelligence that I've reviewed that says things were not where they were supposed to be, moved or otherwise," Mr Hegseth said in an often fiery news conference.
US President Donald Trump, who watched the exchange with reporters, echoed his defence secretary, saying it would have taken too long to remove anything.
"The cars and small trucks at the site were those of concrete workers trying to cover up the top of the shafts. Nothing was taken out of (the) facility," he wrote on social media, without providing evidence.
Several experts cautioned this week that Iran likely moved a stockpile of near weapons-grade highly enriched uranium out of the deeply buried Fordow site before the strikes.
They also said that the country could be hiding it and other nuclear components in locations unknown to Israel, US and United Nations nuclear inspectors.
The experts noted satellite imagery from Maxar Technologies showing "unusual activity" at Fordow on Thursday and Friday, with a long line of vehicles waiting outside an entrance to the facility.
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A senior Iranian source said on Sunday that most of the 60% highly enriched uranium had been moved to an undisclosed location before the US attack.
The Financial Times, citing European capitals, reported that Iran's uranium stockpile remains largely intact since it was not concentrated at Fordow.
Mr Hegseth's comments denying such claims came at a news conference where he also accused the media of downplaying the success of the US strikes following a leaked, preliminary assessment from the Defense Intelligence Agency suggesting they may have only set back Iran by months.
He said the analysis was low confidence, and, citing comments from CIA Director John Ratcliffe, said it had been overtaken by intelligence showing that Iran's nuclear programme was severely damaged and would take years to rebuild.
Mr Hegseth described the strikes as "historically successful".
His comments came after Iranian Supreme Leader Ayatollah Ali Khamenei said that Iran would respond to any future US attack by striking American military bases in the Middle East.
The 86-year-old claimed victory over Israel after 12 days of war and promised that Iran would not surrender despite President Trump's calls.
"The American president exaggerated events in unusual ways, and it turned out that he needed this exaggeration," Mr Khamenei said.
The US "has gained nothing from this war," he said, adding that the strikes "did nothing significant" to Iran's nuclear facilities.
"The Islamic republic won and, in retaliation, dealt a severe slap to the face of America" - a reference to Iran's missile launch on Qatar targeting the largest US base in the Middle East.
"I want to congratulate the great Iranian nation ... for its victory over the fallacious Zionist regime," Mr Khamenei added, claiming that Israel had "almost collapsed" because of his country's strikes.
Both Iran and Israel had already claimed they won, with Israeli Prime Minister Benjamin Netanyahu hailing on Tuesday a "historic victory" for Israel.
'In your DNA and in your blood to cheer against Trump', Hegseth tells media
During the news conference, Mr Hegseth criticised the media, without evidence, for having an anti-Trump bias.
"It's in your DNA and in your blood to cheer against Trump because you want him not to be successful so bad," the defence secretary said.
"There are so many aspects of what our brave men and women did that ... because of the hatred of this press corps, are undermined," he said.
President Trump praised the event on his Truth Social platform, describing it as: "One of the greatest, most professional, and most 'confirming' News Conferences I have ever seen!"
On X, Mr Hegseth thanked Mr Trump for his praise.
During the news conference, the top US general largely stuck to technical details, outlining the history of the bunker-busting bombs used.
Chair of the Joint Chiefs of Staff, General Dan Caine, showed a video testing the bombs on a bunker similar to the ones struck in Iran.
He declined to provide his own assessment of the strike and deferred to the intelligence community.
Gen Caine denied being under any pressure to change his assessment to present a more optimistic view of the US strikes.
He also said that he would not change his assessment due to politics. Uniformed military officials are supposed to remain apolitical and provide their best military advice.
"I've never been pressured by the president or the secretary to do anything other than tell them exactly what I'm thinking, and that's exactly what I've done," Gen Caine said.
