"Think of Mojtaba Khamenei as his father on steroids."

That is how Kasra Aarabi, director of Islamic Revolutionary Guard Corps research at the advocacy group United Against Nuclear Iran, described Iran’s new supreme leader in comments to Fox News Digital following reports that the son of Ayatollah Ali Khamenei has been selected to lead the Islamic Republic.

"Mojtaba was already operating as a ‘mini supreme leader’ in the Bayt-e Rahbari — his father’s office and the core nucleus of power in the regime," Aarabi said.

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"His father had created the Bayt’s extensive apparatus as a hidden power structure to ensure continuity should he be eliminated — and through Mojtaba’s appointment, this is exactly what we will get," Aarabi said.

President Donald Trump also reacted to Mojtaba Khamenei’s rise. In an interview with the New York Post, Trump said he was "not happy with" the younger Khamenei replacing his father as leader of Iran’s theocratic system but declined to elaborate on how the United States might respond. "Not going to tell you," Trump said when asked about his plans regarding the new supreme leader. "Not going to tell you. I’m not happy with him."

An Iranian source with knowledge of the leadership transition told Fox News Digital that earlier speculation Mojtaba might pursue reforms now appears unlikely given the circumstances surrounding his appointment.

"Previously there were whispers suggesting that if Mojtaba were to become the leader, he might introduce reforms that would both open up the domestic political space and bring a more interactive approach to foreign policy," the source said.

"However, now this possibility seems very weak."

Mojtaba was chosen "amid disputes, controversies, and pressure from the IRGC," according to the source, meaning he "owes his appointment to their support and therefore cannot act against their wishes."

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Mojtaba Khamenei, 56, has spent decades building influence inside the power structures surrounding Iran’s supreme leader.

Born in 1969 in Mashhad, he pursued clerical studies in Tehran, Iran, after the 1979 Islamic Revolution that brought his father to prominence. Over time, however, analysts say his influence developed less through traditional clerical authority and more through Iran’s security institutions.

In 2019, the United States sanctioned Mojtaba under Executive Order 13867. The U.S. Treasury Department said he had been "representing the supreme leader in an official capacity despite never being elected or appointed to a government position aside from work in the office of his father."

Behnam Ben Taleblu, senior director of the Foundation for Defense of Democracies' Iran Program, said Mojtaba’s background reflects a broader shift inside the Islamic Republic.

"Despite donning a turban, Mojtaba is the product of the regime’s national security deep state," Ben Taleblu told Fox News Digital. "Expect him to work with and through the IRGC to keep his hold on power."

Aarabi said Mojtaba has spent years consolidating influence behind the scenes.

"His past tells us he enjoys micromanaging every aspect of authority to satisfy his thirst for power," Aarabi said, describing how Mojtaba allegedly relocated IRGC command centers to his office during protests, engineered election outcomes and installed loyalists across state institutions.

Since 2019, Aarabi added, Mojtaba has also been implementing what he described as his father’s effort to "purify" the regime by promoting ideological loyalists across the political system.

"Mojtaba is a deeply antisemitic, anti-American, and anti-Western ideologue," Aarabi said. "He has personally been involved in repression in Iran and terror plots abroad."

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Analysts say Mojtaba’s rise may further strengthen the role of Iran’s security institutions.

"The rise of the younger Khamenei expedites trendlines seen in Iranian politics and national security for years," Ben Taleblu said. "From one Khamenei to another, things in Iran can be expected to go from bad to worse if this regime survives."

"And like the elder Khamenei, corruption runs in the family," he added.

Ben Taleblu warned that the regime may also escalate tensions externally as a survival strategy.

"The regime knows it is weak, but believes it can extract a price and widen a crisis in order to survive," he said.

For opposition groups inside Iran, the leadership transition signals continuity rather than reform.

"He's the son of Khamenei and they have same ideology and they same strategy and they try to continue the same policy," said Khalid Azizi, spokesperson for the Kurdistan Democratic Party of Iran.

"So far it's very difficult to say what he will be done and is he going to have a different policy? I don't expect this."

The Iranian source who spoke with Fox News Digital said that while engagement with the United States and the West is theoretically possible in the future, the chances remain slim.

"As I mentioned," the source said, "this possibility is very weak."

"In short," Aarabi said, "Mojtaba is his father on steroids. He’s certainly no MBS."