Iran's supreme leader has insisted the US "gained no achievements" from strikes on its nuclear facilities, in his first public address since a ceasefire with Israel was agreed on Tuesday.

Ayatollah Ali Khamenei said the strikes did not "accomplish anything significant" to disrupt Iran's nuclear programme, and described the retaliation against an American air base in Qatar as dealing a "heavy blow".

It came as Washington doubled down on its assessment that the strikes had severely undermined Iran's nuclear ambitions.

US Defence Secretary Pete Hegseth said intelligence gathered by the US and Israel indicated the operation "significantly damaged the nuclear programme, setting it back by years".

Previously, US President Donald Trump said the strikes against three key nuclear sites inside Iran "totally obliterated" them, and has responded furiously to reports citing unnamed American officials suggesting the damage may have been less extensive than anticipated.

Speaking alongside senior general Dan Caine at a Pentagon press conference on Thursday morning, Hegseth said the mission was a "historic success" that had "rendered [Iranian] enrichment facilities inoperable".

During an at times combative exchange with reporters, Hegseth also said the US was "not aware of any intelligence" which indicated the enriched uranium had moved out of Fordo - the deeply buried facility which the US targeted with powerful so-called bunker buster bombs - prior to the strikes.

Khamenei, who had been largely out of public view since direct conflict with Israel broke out on 13 June, released a televised address on Thursday morning, ending a week-long public silence.

The supreme leader has reportedly been sheltering in a bunker and limiting communications, which has sparked speculation about his whereabouts. Iranian authorities did not disclose where he was speaking from on Thursday, though a senior official acknowledged he was in a safe place earlier this week.

Khamenei used Thursday's video address to threaten to carry out more strikes on US bases in the Middle East if Iran was attacked again, and declared victory over both Israel and the US.

Khamenei said Trump had "exaggerated" the impact of the nuclear site strikes, adding: "They couldn't accomplish anything and did not achieve their objective."

Referencing the attack on the US air base in Qatar, Khamenei said: "This incident is also repeatable in the future, and should any attack take place, the cost for the enemy and the aggressor will undoubtedly be very high."

No one was killed during that attack, which Trump said had been flagged before it was launched. The US says the base was not damaged.

CBS News, the BBC's US partner, reports that the White House is considering a range of options to entice Iran back to the negotiating table, including facilitating funding for a civilian, non-enrichment nuclear program.

However, Iran's foreign minister told Iranian state TV on Thursday that there no talks with the US are planned.

Direct confrontation broke out between Iran and Israel on 13 June, after Israeli Prime Minister Benjamin Netanyahu said that "if not stopped, Iran could produce a nuclear weapon in a very short time".

A day earlier the global nuclear watchdog's board of governors declared Iran was in breach of its non-proliferation obligations for the first time in 20 years.

Iran has maintained that its nuclear programme is for civilian purposes alone and that it had never sought to develop a nuclear weapon.

On Thursday, Iran approved a parliamentary bill calling for an end to the country's co-operation with the International Atomic Energy Agency (IAEA), meaning it is no longer committed to allowing nuclear inspectors into its sites.

Iran's health ministry said 610 people were killed during the 12 days of air attacks, while Israeli authorities said 28 were killed.

The US became directly involved last weekend, striking facilities in Fordo, Natanz and Isfahan, before Trump sought to rapidly mediate a ceasefire between Israel and Iran, which has held since.

UN nuclear watchdog chief Rafael Grossi said on Wednesday that there was a chance Tehran had moved much of its highly enriched uranium elsewhere as it came under attack.