Members of Malaysia's long ruling party are working on moves to oust embattled prime minister Najib Razak. and have secured the backing of former prime minister Mahathir Mohamad.
Mr Najib is attending a summit in the United States hosted by president Barack Obama.
Dr Mahathir has been declared a patron of the rebel organisation made up of disenchanted branch members of the United Malays National Organisation (UMNO).
Dissent has been growing in the party that has ruled Malaysia since its independence from Britain as Mr Najib, a close ally of successive Australian governments, has been embroiled in a financial scandal allegedly linked to Malaysia's wealth fund 1Malaysia Development Berhad, which he founded and oversees through an advisory committee.
But powerful UMNO division chiefs who have benefited from decades of party largesse are showing no sign of abandoning their support for 62 year-old British educated Mr Najib, who has called on the Muslim majority country to unite and move forward.
Party secretary-general Adnan Mansor dismissed the rebel group as "sh_t-stirrers."
Mr Najib last year removed key party members, including an attorney-general, who were seen as critical of his role in the 1Malaysia scandal.
He also orchestrated the passing of a new security law that gives him unchecked powers to crackdown on all perceived threats to "socio-political stability," including protests.
Dr Mahathir, 91, has been one of Mr Najib's fiercest critics, demanding that he step down for the sake of the party he led for more than 20 years.
The rebels said in a statement they are working to pass resolutions at the branch level to ask Mr Najib to step down.
Investigations are underway in several countries, including by the US Federal Bureau of Investigation, into allegations swirling around the 1Malaysia fund which is US$11 billion in debt and struggling to pay its bankers.
Malaysia's Attorney-General Mohamed Apandi Ali in January cleared Mr Najib of wrongdoing over the transfer of US$700 million into the prime minister's personal bank account in 2013, claiming it was a donation from the Saudi Royal family.
But Mr Najib has refused to clarify what the money was for and what happened to millions of dollars, while insisting he never personally benefited.
Mr Najib is scheduled to speak at the two-day summit that will be attended by leaders of the 10-member Association of South-East Asian Nations (ASEAN) in California, starting on Monday.
US officials have portrayed the summit, the first of its kind on US soil, as a "milestone" in the US's strategic engagement with the region at a time of China's growing assertiveness and concern over rival territorial claims in the resource rich South China Sea.
Human rights groups have criticised the summit, saying it will be seen as an endorsement of repressive regimes.
Only four participating countries – Indonesia, the Philippines, Singapore and Malaysia – will be represented by elected leaders.
