US-based Reza Pahlavi said the death of Iran's supreme leader, Ayatollah Ali Khamenei, on the first day of the war Saturday means the current regime is now "drawing its final breaths."

Pahlavi, who has not returned to Iran since before the 1979 Islamic revolution that ousted the monarchy, is billing himself as the man to lead a democratic transition to a secular Iran, as the theocratic regime fights to survive.

"I ask you, while maintaining your security, to demonstrate your satisfaction with and support for the crushing of the Islamic Republic through nightly chants, and to shout your demands for Iran's future," Pahlavi, 65, wrote on X on the second day of the US and Israeli attacks.

"My strength comes from your strength and your support," he wrote.

Pahlavi urged the "remaining officials of this republic of terror" to hand over power without bloodshed.

And he reached out to Iranians outside the country, asking them to intensify their support for overthrowing the government.

"Force the world to hear the Iranian people's support for this humanitarian intervention and our demand for the complete fall of the regime," Pahlavi wrote.

The war quickly decapitated Iran's theocratic government by killing supreme leader Ayatollah Ali Khamenei and other senior leaders.

The Iranian opposition remains divided and Pahlavi has faced criticism for his support for Israel, making a highly publicized visit in 2023 that fractured an attempt to unify opposition camps.

He has never distanced himself either from his father's autocratic rule.