Follow live updates here
US negotiators concluded that diplomacy with Tehran was futile and that Iran was planning missile attacks on American targets, so it launched strikes against the country, senior administration officials said on Saturday.
Throughout weeks of US-Iran negotiations, Tehran refused to address its ballistic missile programme and insisted on enriching uranium for the purposes of building weapons, senior officials in President Donald Trump's administration said.
This led Mr Trump to decide to join Israel in launching air strikes on Iran. Tehran retaliated with missile attacks across the region.
"The President decided he was not going to sit back and allow American forces in the region to absorb attacks from conventional missiles," one official told journalists on a call.
"We are not going to let them hit us first."
Late on Thursday, the US and Iran ended the third round of "intensive" nuclear talks. A fourth meeting had been scheduled in Vienna next week.
Oman's Foreign Minister Badr Al Busaidi, who had been acting as a go-between, declared "significant progress" after the talks ended.
But Mr Trump had been threatening strikes for weeks, dispatching aircraft carriers in what he called an "armada" of military firepower to the region, ready to strike whenever he gave the order.
The US, in so-called Operation Midnight Hammer, struck three Iranian nuclear sites in June last year, obliterating the country's nuclear programme.
For the US, if Iran were to rebuild, Washington would "address it", officials said, adding that this had been clear to the Iranians during nuclear talks.
US officials said that Iran had been rapidly rebuilding its damaged nuclear infrastructure at Natanz, Fordow and Isfahan after the strike.
In addition, Iran expanded its enrichment programme far beyond civilian needs, and was in "the throes of rebuilding all that had been destroyed".
When US negotiators requested a detailed plan addressing enrichment limits, Iran presented a seven-page document projecting uranium production based on “internal needs” — a plan that, according to one official, would have created enrichment capability that was roughly five times more than laid out in the 2015 Iran nuclear agreement.
During the negotiations, the US had offered the Iranians "free nuclear power forever" in exchange for abandoing their enrichment ambitions.
The Iranians only agreed to do so temporarily.
"They basically said that didn't work for them," the official said. "They needed to enrich uranium. And we basically said, well, that that makes absolutely no sense."
A major concern for the US side was Iran’s capacity to manufacture advanced IR-6 centrifuges — “the fastest ones out there” — and its simultaneous stockpiling of 20 per cent and 60 per cent enriched uranium, which drastically shortens the path to weapons-grade material.
The official said Iranian officials were deceptive when claiming their nuclear material was for medical research when instead it was diverted and accumulated, culminating in roughly 450kg of 60 per cent enriched material - which the official claimed was only one week away from getting to 90 per cent weapons grade.
US officials concluded that Iran's negotiating posture was intended to preserve a nuclear weapons option, rather than accept long-term limits.
“You have to know very quickly if there’s a deal to do or not,” one official said.
Trump administration officials said that they "could have made another short-term bad deal, but it wouldn’t have dealt with the long-term issue of Iran”.
That assessment, according to the officials, formed the rationale behind the administration’s subsequent actions.
In a post on Truth Social on Saturday, Mr Trump announced that Iran's leader Ali Khamenei was dead, calling him "one of the most evil people in history".
"This is not only Justice for the people of Iran, but for all Great Americans, and those people from many Countries throughout the World, that have been killed or mutilated by Khamenei and his gang of bloodthirsty THUGS," Mr Trump wrote.
He called on the Iranian people "to take back" their country.
