Reza Pahlavi, the son of Iran’s former pro-western monarch, has predicted the country’s Islamic regime will fall and claimed he is “uniquely” placed to head a successor government.

His bid to assume the leadership of a possible new Iran follows weeks of mass protests that have left thousands dead after being brutally suppressed by security forces.

His credentials are certain to be challenged by other opponents of Ayatollah Ali Khamenei’s regime, given Pahlavi has not been in Iran since his family fled the country at the beginning of the 1979 Islamic revolution. Many question his level of popular support, even though his name has been chanted at some protests.

Calling on the west to help unseat Khamenei, Iran’s supreme leader, Pahlavi said on Friday that the regime was nevertheless doomed to collapse with or without such assistance.

“The Iranian people are taking decisive actions on the ground, it is now time for the international community to join them fully,” he told reporters at a news conference in Washington.

He said foreign involvement did not require “boots on the ground” but instead “targeted intervention” that could weaken the regime’s repressive apparatus, such as targeting the leadership of the Revolutionary Guards.

“What they need from the world is resolute, targeted support to protect lives, amplify their voices and hasten the collapse that is already on the way,” he said. “But let me be clear, with or without the world’s help, the regime will fall. It will fall sooner, and more lives will be saved if the world turns its words into action.”

Pahlavi said 12,000 protesters had been killed over 48 hours as security forces conducted a bloody crackdown against demonstrations that have swept the country since 28 December. Human rights groups have confirmed lower figures but still put the death toll in thousands.

Donald Trump had vowed that “help is on the way” if the regime continued to kill protesters, or carried out executions of those detained. But he retreated after warnings from the US’s Middle East allies that military intervention could trigger regional instability. Posting on his Truth Social network on Friday, Trump thanked the regime for allegedly cancelling a wave of scheduled executions.

“I greatly respect the fact that all scheduled hangings, which were to take place yesterday (Over 800 of them), have been cancelled by the leadership of Iran. Thank you!” he wrote.

Pahlavi spoke out after protesters chanted his name and “long live the shah” at recent protests – an ironic development given that the monarchical regime of his father, Shah Mohammad Reza Pahlavi, was overthrown after months of similar mass demonstrations and complaints of torture and human rights abuses.

He avoided giving a clear answer when asked by the Guardian if he intended to re-establish a monarchy, but said he had a “comprehensive plan for an orderly transition, which is ready to be implemented immediately”. It would include referendums to establish the form of a successor government, but he refused to rule out a monarchical restoration.

“I am uniquely positioned to ensure a stable transition,” he said “That’s the verdict delivered loudly and clearly by the people in the face of bullets.”

He claimed “large segments” of the security forces had already refused to fire on the population and “whispered their loyalty to me”.

He referred to “the bond between me and the Iranian people” – a phrase redolent of his father’s rhetoric – and said: “It’s been with me since birth, and it cannot be broken, even in exile.”