Doubts about whether exiled Iranian dissident Reza Pahlavi could muster sufficient support within Iran to take over the country’s leadership, United States President Donald Trump has expressed, while leaving open the possibility of the collapse of Tehran’s theocratic regime.

In a statement to Reuters, Donald Trump described Reza Pahlavi as “very likable”, but stressed that he was unsure whether he could secure the acceptance of Iranians should he attempt to lead the country after a potential political transition.

“He seems very likable, but I don’t know how he would be received within his own country,” the US president said from the Oval Office. “And, frankly, we haven’t gotten to that point yet. I don’t know if his country would accept his leadership and, of course, if they did, that would be acceptable to me.”

Trump also noted that there is a possibility that the mullahs’ regime in Iran could collapse, but did not go into specific assessments of the timing or developments that could lead to such a development.

Although he has repeatedly threatened to intervene in support of anti-government protests in Iran, the U.S. president appeared cautious on Wednesday about giving full political support to Reza Pahlavi, son of Iran’s last Shah, who was overthrown in the 1979 Islamic Revolution.

Trump’s statements add to the controversy surrounding Pahlavi’s potential to play a leadership role in a transitional period in Iran, particularly after the US president said last week that he did not intend to meet him.

Reza Pahlavi, 65, lives in the United States and has been out of Iran since before his father’s overthrow. In recent years, he has emerged as one of the most prominent voices of the Iranian opposition abroad, actively supporting anti-government protests and recently calling on protesters to rise up and pledging to return to the country.