US President Donald Trump on Wednesday said the United States would hold nuclear talks with Iran next week, teasing the possibility of a deal even after boasting that recent US strikes had crippled the Islamic republic's atomic programme.

Trump credited the unprecedented US attacks with the "total obliteration" of Iran's nuclear capabilities, and said they had set the country's programme back "decades".

But leaked US intelligence cast doubt on that assessment, saying the strikes had likely delayed Tehran by just a few months.

Before the agreement of a ceasefire on Tuesday, Israel had pounded Iranian nuclear and military sites over the course of 12 days of war, while Iran launched waves of missiles at its regional arch foe in their deadliest-ever confrontation.

The United States joined the fray in support of its ally, hitting two nuclear facilities with massive bunker-buster bombs over the weekend, while a guided missile from a submarine struck a third.

"They're not going to be building bombs for a long time," said Trump, adding that the ceasefire that he declared was going "very well".

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

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

Iranian President Masoud Pezeshkian had said on Tuesday his country was willing to return to negotiations over its nuclear programme, but that it would continue to "assert its legitimate rights" to the peaceful use of atomic energy.

Israel's military said Wednesday it was "still early" to assess the damage the war caused to Iran's nuclear programme.

"I believe we have delivered a significant hit to the nuclear programme, and I can also say that we have delayed it by several years," said Israeli military spokesman Effie Defrin.

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

But US media on Tuesday cited people familiar with a Defense Intelligence Agency report as saying the American strikes did not fully eliminate Iran's centrifuges or enriched uranium stockpiles.

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

Israel had said its bombing campaign, which began on June 13, was aimed at preventing Iran from acquiring a nuclear weapon, an ambition Tehran has consistently denied.

Israeli Prime Minister Benjamin Netanyahu, in an address to the nation after the ceasefire, announced that "we have thwarted Iran's nuclear project".

"And if anyone in Iran tries to rebuild it, we will act with the same determination, with the same intensity, to foil any attempt," he said. (AFP)