Jeffrey Bomanak (middle) takes oath with a Free Papua Movement (OPM) leader Jacob Prai (right) in Sweden in 2017. Photo: Supplied
Australia says it "unreservedly recognises Indonesia's territorial integrity and sovereignty over the Papua provinces" in response to a letter accusing it of betrayal, but it also "condemns violence".
The Organisasi Papua Merdeka (OPM) - Free Papua Movement - has laid into the US and Australian leaders.
OPM leader Jeffrey Bomanak wrote to US President Joe Biden and Australia's Prime Minister Anthony Albanese, saying West Papua is "filled with Indonesia's barbarity".
The White House did not respond to a request for comment.
Bomonak spoke of Papua's past support for US troops but that it had not been reciprocated.
"As Australian and American leaders, your Remembrance Day is a commemoration of a tradition of loyalty and sacrifice that you have failed to honour.
"If you cannot stand by those who stood by you, then your idea of 'loyalty' and 'remembrance' being something special is a myth, a fairy tale.
"There is nothing special in treachery."
Bomanak wrote of the two countries' "betrayal" and their support of Indonesia, including an RAAF Hercules transporting 600 Indonesian military "to slaughter us on Biak Island" in 1998, and logistics for "slaughter and bombing of our highland villages".
"You were silent about the 1998 roll of film depicting victims of the Biak Island massacre.
"In 1969, to help prevent our decolonisation, you placed two of our leaders on Manus Island instead of allowing them to reach the United Nations in New York - an act of shameless appeasement as a criminal accomplice to a mass-murderer.
"Every single act and action of your betrayal contravenes Commonwealth and US Criminal Codes, and violates the UN Charter, the Genocide Act, and the Torture Convention."
A spokesperson for Australia's Department of Foreign Affairs and Trade said its recognition of Indonesia's territorial integrity and sovereignty is a longstanding and bipartisan position, and is consistent with the Lombok Treaty.
"Our two countries enjoy a strong and close relationship allowing us to discuss sensitive issues including the situation in Indonesia's Papua," the spokesperson said.
"We recognise the complexity of the security situation in Papua and condemn violence, affecting civilians and authorities alike.
"We make clear that credible reports of human rights abuses should be investigated thoroughly."
Australia says it provides support for broader development objectives in Papua through its development cooperation program, and assists the Indonesian government to better channel its resources to reduce poverty, improve basic services and increase citizen participation in Papua.