US President Donald Trump on Thursday insisted he should have a role in picking Iran’s next supreme leader after the killing of Ali Khamenei, whose son he said he found unacceptable.

"Khamenei's son is a lightweight. I have to be involved in the appointment, like with Delcy," Trump told Axios in an interview, drawing a comparison to Venezuela, where interim President Delcy Rodriguez has cooperated with him under threat of violence after the United States ousted her boss, Nicolas Maduro.

Trump told the news outlet that the United States would likely return to war within five years without a favourable leader in Iran.

"Khamenei's son is unacceptable to me. We want someone that will bring harmony and peace to Iran," Trump was quoted saying by the news outlet.

Role unclear

It was unclear in what way Trump would be able to take a role in Iran's selection of a new supreme leader, a decision made by an assembly of senior clerics mostly staunchly opposed to the United States.

Ali Khamenei, who ruled Iran since 1989, was killed on Saturday in a joint US-Israeli strike on Tehran.

His son, Mojtaba Khamenei, is considered one of the contenders to succeed his father, who was only the second supreme leader after revolutionary leader Ruhollah Khomeini.