US forces struck three Iranian nuclear sites in a "very successful attack," President Donald Trump said on Saturday (local time), adding that Tehran's nuclear programme had been "obliterated".
After days of deliberation, Trump's decision to join Israel's military campaign against its major rival Iran represents a major escalation of the conflict.
"The strikes were a spectacular military success," Trump said in a televised Oval Office address. "Iran's key nuclear enrichment facilities have been completely and totally obliterated."
In a speech that lasted just over three minutes, Trump said Iran's future held "either peace or tragedy," and that there were many other targets that could be hit by the US military.
"If peace does not come quickly, we will go after those other targets with precision, speed and skill."
The US reached out to Iran diplomatically on Saturday to say the strikes were all the US planned, and it did not aim for regime change, CBS News reported.
Trump said US forces struck Iran's three principal nuclear sites: Natanz, Isfahan and Fordow. He told Fox News six bunker-buster bombs were dropped on Fordow, while 30 Tomahawk missiles were fired against other nuclear sites.
U.S. B-2 bombers were involved in the strikes, a U.S. official told Reuters, speaking on condition of anonymity.
"A full payload of BOMBS was dropped on the primary site, Fordow," Trump posted. "Fordow is gone."
"IRAN MUST NOW AGREE TO END THIS WAR," he added.
Reuters had reported earlier on Saturday the movement of the bombers, which can be equipped to carry massive bombs that experts say would be needed to strike Fordow, which is buried under a mountain.
An Iranian official, cited by Tasnim news agency, confirmed that part of the Fordow site was attacked by "enemy airstrikes."
Israeli Prime Minister Benjamin Netanyahu congratulated Trump on his "bold decision" which he said will change history.
"History will record that President Trump acted to deny the world's most dangerous regime, the world's most dangerous weapons," Netanyahu said.
The strikes came as Israel and Iran have been engaged in more than a week of aerial combat that has resulted in deaths and injuries in both countries.
Israel launched the attacks on Iran saying that it wanted to remove any chance of Tehran developing nuclear weapons. Iran says its nuclear programme is for peaceful purposes only.
Diplomatic efforts by Western nations to stop the hostilities have been unsuccessful.
In recent days, Democratic lawmakers and some Republicans have argued that Trump must receive permission from the US Congress before committing the US military to any combat against Iran.
Republican Senate Armed Services Committee Chairman Roger Wicker of Mississippi applauded the operation but cautioned that the U.S. now faced "very serious choices ahead."
Senate Foreign Relations Committee Chairman Jim Risch, a Republican, said that despite the heavy US bombings over Iran, "This war is Israel's war, not our war."
He added, "There will not be American boots on the ground in Iran."
One Republican lawmaker, Representative Thomas Massie of Kentucky, simply said, "This is not constitutional."
Democratic Senator Tim Kaine of Virginia said the US public "is overwhelmingly opposed to the US waging war on Iran" and accused Trump of displaying "horrible judgment".
Israeli military officials said earlier on Saturday that they had completed another series of strikes in southwestern Iran, having targeted dozens of military targets.
Israel launched attacks on June 13, saying Iran was on the verge of developing nuclear weapons. Israel is widely assumed to possess nuclear weapons, which it neither confirms nor denies.
At least 430 people have been killed and 3500 injured in Iran since Israel began its attacks, Iranian state-run Nour News said, citing the health ministry.
In Israel, 24 civilians have been killed by Iranian missile attacks, according to local authorities, in the worst conflict between the longtime enemies. More than 450 Iranian missiles have been fired towards Israel, according to the Israeli prime minister's office.
Israeli officials said 1272 people have been injured since the beginning of the hostilities, with 14 in serious condition.
