Washington (AFP) - US Secretary of State Mike Pompeo plans on Sunday to urge members of the Iranian diaspora to "support" protesters in Iran, as the Trump administration hints at a desire for regime change in Tehran after turning its back on the Iranian nuclear accord.

President Donald Trump -- who has made the Islamic republic a favorite target since his unexpected rapprochement with North Korea -- decided on May 8 to restore all the sanctions that had been lifted as part of the multi-nation agreement aimed at preventing Iran from developing nuclear weapons.

Following the US withdrawal that stunned even Washington's closest European allies, Pompeo on May 21 unveiled a "new strategy" intended to force Iran to yield to a dozen stringent demands or else face the "strongest sanctions in history."

The next US step is due at 6:00 pm Sunday (0100 GMT Monday) in the Ronald Reagan presidential library in Simi Valley, California, when the secretary of state delivers a speech entitled "Supporting Iranian Voices."

With the 40th anniversary of the Islamic Revolution of 1979 a year away, Pompeo plans to retrace "40 years of stealing from the Iranian people, the terrorism they have committed around the region, the brutal repression at home" as well as the "religious persecution" there, a senior State Department official told reporters ahead of the speech.

The venue for Pompeo's address is significant, the official noted: some 250,000 Iranian-Americans live in Southern California.

"He will be exposing some of the corruption" of a "kleptocratic regime," the diplomat told reporters. "The regime has prioritized its ideological agenda over the welfare of the Iranian people."

- 'Demands for a better life' -

Pompeo launched his campaign against Iran on Twitter last month, saying the government in Tehran and the Revolutionary Guards -- the regime's elite armed corps -- had "plundered the country's wealth" in proxy wars "while Iranian families struggle."

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The Trump administration's strategy appears simple: to exploit the already growing tensions within Iranian society that are being exacerbated by renewed US sanctions that have forced some foreign firms to leave.

There have been a series of anti-government protests in Iran in recent months, prompted by an array of different issues and concerns.

The State Department briefer said Pompeo plans to support "the legitimate demands of the Iranian people, especially their economic demands for a better life."

But how far will he and the administration go?

"That's the key question," Behnam Ben Taleblu of the conservative pressure group Foundation for Defense of Democracies (FDD), told AFP. "Pompeo and the administration can do more than just rhetorical support to the Iranian protester."

- How far will the US go? -

Several Iranian dissidents have written to Pompeo to urge him to re-establish punitive measures against the state-owned Islamic Republic of Iran Broadcasting network, which they accuse of abetting human rights violations.

Word of Pompeo's planned speech has fanned speculation on Washington's precise intentions.

The State Department insists that the US seeks merely a "change in behavior" by the regime.

But some senior members of the Trump administration -- notably national security advisor John Bolton -- have made it clear in the past that they would like to see the Tehran regime topple, and Pompeo himself said in May that "the Iranian people get to choose for themselves the kind of leadership they want."

To Behnam Ben Taleblu, "genuine regime change can only come from inside."

With an upsurge of "Iranians of all different social classes protesting," he said, the Trump administration will have to decide whether it wants to "support elements that actually want to change the regime."

Diplomats and experts in Washington are divided as to whether the protests and social tensions within Iran pose a true threat to the Islamic republic.

Nor is there agreement on what it would actually mean should the Iranian regime fall -- but some find that uncertainty deeply worrying.

"The more likely result of regime collapse would be a military coup in the name of restoring order, led by the man Washington’s Iran hawks fear the most: Gen. Qasem Suleimani," the commander of the Revolutionary Guards, according to Mark Fitzpatrick of the International Institute for Strategic Studies.

"Exerting maximum pressure on Iran could bring about America’s worst nightmare," he added on Twitter.