Rubio said there were internal "fractures" inside the Islamic republic and that the United States hopes figures with "power to deliver" take charge.

"We are hopeful that that's the case," Rubio told the ABC News program "Good Morning America."

"There are clearly people there talking to us in ways that previous people in charge in Iran have not spoken to us in the past, some of the things they're willing to do," he said.

Rubio nonetheless also denounced the Islamic republic in broad strokes, insisting that the war aimed to end its nuclear weapons building capacity, which President Donald Trump said he accomplished during an attack last year.

"These people are lunatics. They are insane. They are religious zealots who can never be allowed to possess a nuclear weapon because they have an apocalyptic vision of the future," Rubio said.

Iran denies seeking a nuclear weapon and the UN nuclear watchdog has said no bomb was imminent.

Rubio's comments came a day after Trump said that Iran has already gone through "regime change," one month into the war launched by the United States and Israel.

Trump said that the United States was speaking to a "whole different group of people" and that they were "very reasonable."

On the first day of the war Israel assassinated Iran's longtime supreme leader, Ayatollah Ali Khamenei, and subsequent strikes have killed other top leaders.

Rubio said that there was a difference between private and public messages coming from Iran.

"Obviously they're not going to put it out in press releases, and what they say to you or put out there for the world doesn't necessarily reflect what they're saying in our conversations," Rubio said.

Despite the Trump administration's public talk of diplomacy, the United States has been reinforcing its military presence in the region and Trump on Monday threatened to "blow up" Iran's oil-exporting island of Kharg if purported talks fail.

The comments from the administration signal a readiness to work with some form of the Islamic republic, after the United States and Israel at the start of the war spoke of toppling the government which weeks earlier killed thousands of people as it crushed mass protests.