WASHINGTON — President Donald Trump announced on Saturday that the U.S. military targeted three sites in Iran, effectively joining Israel’s initiative to dismantle the nation’s nuclear program. This bold move aims to undermine a longstanding adversary while grappling with Tehran’s threats of retaliation, which could potentially ignite a broader regional conflict.

There was no immediate acknowledgment from Iran of any strikes being carried out.

This decision to actively involve the U.S. follows over a week of Israeli attacks on Iran, aiming to systematically dismantle the country’s air defenses and missile capabilities while damaging its nuclear enrichment sites. U.S. and Israeli officials have stated that American stealth bombers, equipped with a 30,000-pound (13,500-kilogram) bunker buster bomb, offer the best chance to destroy the heavily-fortified subterranean facilities crucial to Iran’s nuclear program.

“We have completed our very successful attack on the three Nuclear sites in Iran, including Fordow, Natanz, and Esfahan,” Trump said in a post on social media. “All planes are now outside of Iran air space. A full payload of BOMBS was dropped on the primary site, Fordow. All planes are safely on their way home.”

Trump added in a later post that he would address the national at 10:00 p.m. eastern time, writing “This is an HISTORIC MOMENT FOR THE UNITED STATES OF AMERICA, ISRAEL, AND THE WORLD. IRAN MUST NOW AGREE TO END THIS WAR. THANK YOU!”

Trump said B-2 stealth bombers were used but did not specify which types of bombs were dropped. The White House and Pentagon did not immediately elaborate on the operation.

The strikes are a perilous decision for the U.S. as Iran has pledged to retaliate if it joined the Israeli assault, and for Trump personally, having won the White House on the promise of keeping America out of costly foreign conflicts and scoffed at the value of American interventionism.

Trump told reporters on Friday that he was not interested in sending ground forces into Iran. He had previously indicated that he would make a final choice over the course of two weeks, a timeline that seemed drawn out as the situation was evolving quickly.

Iran’s Supreme Leader Ayatollah Ali Khamenei warned on Wednesday the United States that strikes targeting the Islamic Republic will “result in irreparable damage for them.” And Iranian Foreign Ministry spokesman Esmail Baghaei declared “any American intervention would be a recipe for an all-out war in the region.”

Trump has vowed that he would not allow Iran to obtain a nuclear weapon and he had initially hoped that the threat of force would bring the country’s leaders to give up its nuclear program peacefully.

Israel ‘s military said Saturday it was preparing for the possibility of a lengthy war, while Iran’s foreign minister warned before the U.S. attack that American military involvement “would be very, very dangerous for everyone.”

The prospect of a wider war threatened, too. Iranian-backed Houthi rebels in Yemen said they would resume attacks on U.S. vessels in the Red Sea if the Trump administration joins Israel’s military campaign. The Houthis paused such attacks in May under a deal with the U.S.

The U.S. ambassador to Israel announced the U.S. had begun “assisted departure flights,” the first from Israel since the Hamas-led attack on Oct. 7, 2023, that sparked the war in Gaza.

But Trump appears to have made the calculation – at the prodding of Israeli officials and many Republican lawmakers – that Israel’s operation had softened the ground and presented a perhaps unparalleled opportunity to set back Iran’s nuclear program, perhaps permanently.

The Israelis say their offensive has already crippled Iran’s air defenses, allowing them to already significantly degrade multiple Iranian nuclear sites.

But to destroy the Fordo nuclear fuel enrichment plant, Israel has appealed to Trump for U.S. bunker-busting bombs, the 30,000-pound GBU-57 Massive Ordnance Penetrator, which uses its weight and sheer kinetic force to reach deeply buried targets and then explode. The penetrator is currently only delivered by the B-2 stealth bomber, which is only found in the American arsenal.

The bomb carries a conventional warhead, and is believed to be able to penetrate about 200 feet (61 meters) below the surface before exploding, and the bombs can be dropped one after another, effectively drilling deeper and deeper with each successive blast.

The International Atomic Energy Agency has confirmed that Iran is producing highly enriched uranium at Fordo, raising the possibility that nuclear material could be released into the area if the GBU-57 A/B were used to hit the facility.

Previous Israeli strikes at another Iranian nuclear site, Natanz, on a centrifuge site have caused contamination only at the site itself, not the surrounding area, the IAEA has said.

Trump’s decision for direct U.S. military intervention comes after his administration made an unsuccessful two-month push – including with high-level, direct negotiations with the Iranians – aimed at persuading Tehran to curb its nuclear program.

For months, Trump said he was dedicated to a diplomatic push to persuade Iran to give up its nuclear ambitions. And he twice – in April and again in late May – persuaded Israeli Prime Minister Benjamin Netanyahu to hold off on military action against Iran and give diplomacy more time.

The U.S. in recent days has been shifting military aircraft and warships into and around the Middle East to protect Israel and U.S. bases from Iranian attacks.

All the while, Trump has gone from publicly expressing hope that the moment could be a “second chance” for Iran to make a deal to delivering explicit threats on Khamenei and making calls for Tehran’s unconditional surrender.

“We know exactly where the so-called ‘Supreme Leader’ is hiding,” Trump said in a social media posting. “He is an easy target, but is safe there – We are not going to take him out (kill!), at least not for now.”

The military showdown with Iran comes seven years after Trump withdrew the U.S. from the Obama-administration brokered agreement in 2018, calling it the “worst deal ever.”

The 2015 deal, signed by Iran, U.S. and other world powers, created a long-term, comprehensive nuclear agreement that limited Tehran’s enrichment of uranium in exchange for the lifting of economic sanctions.

Trump decried the Obama-era deal for giving Iran too much in return for too little, because the agreement did not cover Iran’s non-nuclear malign behavior.

Trump has bristled at criticism from some of his MAGA faithful, including conservative pundit Tucker Carlson, who have suggested that further U.S. involvement would be a betrayal to supporters who were drawn to his promise to end U.S. involvement in expensive and endless wars.

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Rising reported from Dubai, United Arab Emirates. Associated Press writers Mehmet Guzel in Istanbul; Josef Federman in Jerusalem; Samy Magdy in Cairo; Matthew Lee and Josh Boak in Washington, D.C.; and Farnoush Amiri and Jon Gambrell in Dubai contributed to this report.