By Kevin Liptak, CNN

(CNN) — The United States decisively entered into conflict with Iran on Saturday after President Donald Trump ordered US warplanes to drop massive bombs on three nuclear sites inside the country, thrusting him squarely into an escalating Middle East conflict even as he holds out hope the matter can be resolved diplomatically.

In social media posts and during a late-night address from the White House, Trump described the bombings as entirely successful and warned Iran against retaliation.

“Our objective was the destruction of Iran’s nuclear enrichment capacity and a stop to the nuclear threat posed by the world’s No. 1 state sponsor of terror,” Trump said during his four-minute speech from the White House Cross Hall.

He described the mission as a “spectacular military success” and called on Iran to immediately return to diplomatic efforts to end the conflict. He said the sites had been “totally obliterated.”

“Iran, the bully of the Middle East, must now make peace,” Trump said, flanked by his vice president, secretary of state and defense secretary. “If they do not, future attacks will be far greater and a lot easier.”

The US strikes on the Iranian nuclear sites, which Trump identified earlier as Fordow, Natanz and Isfahan, significantly ratchet up tensions in the country, and amounts to one of the most consequential choices of Trump’s young second presidency. The debate over whether to target Iran directly had divided Trump’s political coalition, with concerns high among some members of the Republican base that intervening could drag the US into a new, prolonged conflict.

The US used six B-2 bombers to drop a dozen “bunker buster” bombs on the Fordow nuclear site, a US official told CNN. Trump said in a message on social media that “a full payload of BOMBS was dropped on the primary site, Fordow.”

“There is not another military in the World that could have done this,” Trump wrote. “NOW IS THE TIME FOR PEACE!”

The bombs used in the strikes were GBU-57A/B Massive Ordnance Penetrators, known as a “bunker busters,” two sources familiar with the operation said. Experts have highlighted them as the only type of bomb potentially capable of destroying Iran’s underground Fordow nuclear facility.

The MOP — a 30,000-pound bomb with 6,000 pounds of explosives — was designed for “reaching and destroying our adversaries’ weapons of mass destruction located in well-protected facilities,” according to a fact sheet from the US Air Force. Saturday is the first known instance of the bomb being used operationally.

The move to target the Fordow facility in particular, which successive US presidents had considered but ultimately decided against, will now insert Trump directly into a growing crisis that he had once hoped to defuse through diplomacy.

The decision to target Iran directly came days after the White House announced Trump would allow for two weeks to determine whether diplomacy was possible to resolve the conflict.

It’s the first time in several decades — since the Iranian revolution in 1979 — that an American president has deployed Air Force assets to target major facilities in the country.

In his remarks Saturday night, Trump described himself as a longtime opponent of allowing Iran to obtain a nuclear weapon.

“I decided a long time ago that I will not let this happen,” he said.

The US gave Israel a heads-up on its strikes before launching them, two officials familiar with the matter told CNN. Trump and Israeli Prime Minister Benjamin Netanyahu also spoke Saturday evening following the strikes, two White House officials said.

Trump said during his speech that he and Netanyahu had worked closely to coordinate the attacks in Iran. The Israeli leader praised Trump’s decision, saying it will “change history.”

“President Trump, I thank you. The people of Israel thank you,” Netanyahu said in a statement.

As Trump was mulling his decision, Iran had vowed to retaliate to any US aggression, and American military assets had begun massing in the region to prepare for any retaliatory action from Tehran. After his address to the nation, Trump issued a stark warning to Iran, saying any retaliation will be met with “far greater” force than the Saturday strikes.

Trump appears hopeful the strikes will propel Tehran back to negotiations, and there were no plans for additional US actions inside Iran on Saturday evening as he presses Iranian leaders to “agree to end this war,” according to sources familiar with the matter.

Trump had come to believe over the last several days that US forces were necessary to taking out Iran’s highly fortified nuclear facilities, and made the decision when it seemed clear that diplomacy remained deadlocked.

US officials had come to believe Iran was not ready to strike a satisfactory nuclear deal after Europeans leaders met with their Iranian counterparts in Geneva on Friday, two sources familiar with the matter told CNN.

Iran’s foreign minister said after the Geneva meeting that Iran would not sit down with the United States without Trump asking Netanyahu to stop Israel’s attacks, which was not something the president was willing to do, the sources said.

This story has been updated with additional information.

CNN’s Alayna Treene and Kristen Holmes contributed to this report.