Tehran, Iran - Iran's Supreme Leader Ayatollah Ali Khamenei on Thursday said US President Donald Trump "exaggerated" the impact of US strikes on nuclear sites in the country.

In his first appearance since a ceasefire with Israel took effect, he hailed his country's "victory" and vowed never to surrender to the US, while claiming that Washington had been dealt a "slap" after striking Iranian nuclear sites.

The remarks came amid growing doubts over the actual extent of the damage inflicted by American strikes on key Iranian nuclear sites during the war launched without provocation by Israel.

"The American president exaggerated events in unusual ways, and it turned out that he needed this exaggeration," Khamenei said.

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The US "has gained nothing from this war," he said, adding that Sunday's 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," he said, a reference to Iran's missile launch 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," he added, claiming that Israel had "almost collapsed" because of Iran'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 the US, leaked intelligence this week raised some big question marks over the Trump administration's bombastic claims to have "completely destroyed" Iran's nuclear program.

An initial classified assessment, first reported by CNN, was said to have concluded that the strikes did not destroy key components and that Iran's nuclear capabilities were set back only months at most.

Another key question raised by experts is whether Iran, preparing for the strike, moved out some almost 900 pounds of enriched uranium, which could now be hidden elsewhere in the vast country.

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The Trump administration has hit back furiously, with the president saying the attack "obliterated" Iran's nuclear facilities, including the key site of Fordow buried inside a mountain.

Trump said that Hegseth, whom he dubbed "war" secretary, would hold a news conference at 8 Thursday to "fight for the dignity of our great American pilots".

CIA chief John Ratcliffe said in a statement on Wednesday that "several key Iranian nuclear facilities were destroyed and would have to be rebuilt over the course of years."

Iranian foreign ministry spokesman Esmaeil Baqaei admitted to Al Jazeera that "nuclear installations have been badly damaged, that's for sure."

Trump, who is now seeking to restart the negotiations the US and Israel previously blew up, said discussions with Tehran would be held next week, with his special envoy Steve Witkoff expressing hope "for a comprehensive peace agreement."

Trump told reporters that Israel and Iran were "both tired, exhausted", before going on to say that talks were planned with Iran next week.

"We may sign an agreement. I don't know," he added.

Iran has systematically denied seeking a nuclear weapon while defending its legitimate rights to the peaceful use of atomic energy under the Nuclear Non-Proliferation Treaty, of which it is a signatory.

Israel – an undeclared nuclear power which has heavily bombed five of its neighbors over the past 21 months and faces accusations of genocide in Gaza – is not.