WASHINGTON, Feb. 28 (Xinhua) -- U.S. President Donald Trump said early Saturday morning that the U.S. forces are carrying out a "massive and ongoing" attack on Iran to eliminate "imminent threats from the Iranian regime."

In a video message on his social media platform Truth Social, Trump claimed that Iran threatens the United States and its core national security interests.

Trump said U.S. forces will "destroy their missiles and raze their missile industry to the ground" and "annihilate their navy," while calling on Iranians to "take over your government" after U.S. military operations conclude.

Trump accused Iran of developing "long-range missiles that can now threaten our very good friends and allies in Europe, our troops stationed overseas and could soon reach the American homeland."

However, sources told CNN that Trump's assertion is not backed up by U.S. intelligence.

Trump said that Iran had sought to reach a deal to avoid the conflict, but talks had been unproductive.

"We warned them never to resume their malicious pursuit of nuclear weapons, and we sought repeatedly to make a deal. We tried," he said.

"They rejected every opportunity to renounce their nuclear ambitions, and we can't take it anymore," Trump said. "I will say it again. They can never have a nuclear weapon."

Trump also urged Iranian officials to "lay down your arms," warning, "or you will face certain death."

Meanwhile, Trump acknowledged that the attack on Iran could result in U.S. casualties. "We may have casualties," he said. "That often happens in war."

Jack Reed, the top Democrat on the U.S. Senate Armed Services Committee, said the Trump administration didn't provide Congress with any "real briefings or intelligence" before launching the massive military operations in Iran.

"The president barely mentioned Iran during the longest State of the Union speech in history. He failed to define the objective," Reed said in a statement. "It is hard to justify action without rationale."

Thomas Massie, a Republican lawmaker from Kentucky, criticized the strikes on Iran as "acts of war unauthorized by Congress" in a social media post.

Ruben Gallego, a Democratic Senator from Arizona and former Marine who had served in Iraq, said on social media that Americans should not have to "pay the ultimate price for regime change and a war that hasn't been explained or justified to the American people."

The Pentagon dubbed the massive military strikes "Operation Epic Fury," formalizing it as a major U.S. military operation.

Saturday's strikes involved a mix of U.S. aircraft and Tomahawk cruise missiles fired by U.S. Navy ships in the Middle East, ABC News cited a U.S. official as saying.

U.S. embassies in Israel, Qatar and Bahrain have warned personnel to take shelter.

The U.S. strikes took place from both air and sea and could last for several days, according to multiple U.S. media reports, citing U.S. officials.

The strikes against Iran came on the heels of the latest round of indirect U.S.-Iran nuclear talks in Geneva on Thursday, and additional technical talks have been scheduled for Monday in Vienna.

Before launching the strikes, the Trump administration built up the U.S. military presence in the Middle East to its largest level since the 2003 invasion of Iraq. ■