LONDON and NEW YORK — President Donald Trump said that the U.S. military has begun “major combat operations” in Iran and calling on the Iranian people to rise up and seize the opportunity for regime change.

“Our objective is to defend the American people by eliminating imminent threats from the Iranian regime, a vicious group of very hard, terrible people,” Trump said in a video statement on Truth Social early Saturday morning.

The “massive” operation comes as the U.S. has been trying to negotiate with Iran over its nuclear and missile programs and hours after Trump said he was “not happy with the negotiation.”

And it comes amid questions about the potential justification for a U.S. strike on Iran since Trump has said the Iranian nuclear weapons program was “obliterated” in a U.S. strike last year.

“Its menacing activities directly endanger the United States, our troops, our bases overseas and our allies throughout the world. For 47 years, the Iranian regime has chanted “death to America” and waged an unending campaign of bloodshed and mass murder targeting the United States, our troops and the innocent people in many, many countries,” Trump said.

The military operation against Iran was a preemptive joint attack by the United States and Israel and could last several days, U.S. officials said, with potential targets including Islamic Revolutionary Guard Corps military sites, government buildings, Iranian intelligence assets and defense installations.

“Iran is the world’s number one state sponsor of terror and just recently killed tens of thousands of its own citizens on the street as they protested,” Trump said. “It has always been the policy of the United States, in particular my administration, that this terrorist regime can never have a nuclear weapon. I will say it again. They can never have a nuclear weapon.”

Trump, who campaigned on a message of keeping the U.S. out of foreign entanglements, gravely suggested that “the lives of courageous American heroes may be lost, and we may have casualties.”

“That often happens in war. But we are doing this not for now, we are doing this for the future and it is a noble mission,” Trump continued.

At the end of his message, Trump called on the Iranian people to seize this opportunity for regime change.

“Finally, to the great, proud people of Iran, I say tonight that the hour of your freedom is at hand,” Trump said.

He added, “When we are finished, take over your government. It will be yours to take. This will be probably your only chance for generations.”

Appearing to speak to the Iranian people, Trump said: “No president was willing to do what I am willing to do tonight. Now you have a president who is giving you what you want, so let’s see how you respond. America is backing you with overwhelming strength and devastating force. Now is the time to seize control of your destiny and to unleash the prosperous and glorious future that is close within your reach.”

Meanwhile, some Democratic members of Congress have begun demanding answers.

Rep. Jared Moskowitz (D.-FL) said on social media that he is “formally requesting” that the State Department and Department of War “fully brief Congress on the rapidly evolving situation in Iran.”

Senator Ruben Gallego (D.-Ariz.), a Marine veteran, also posted on X, saying “I lost friends in Iraq to an illegal war. Young working-class kids should not pay the ultimate price for regime change and a war that hasn’t been explained or justified to the American people.”