Australia, Indonesia and Papua New Guinea (PNG) convened their first trilateral defense ministers’ meeting in December 2025. The historic gathering in Port Moresby, PNG, reflects a growing recognition that their shared region, challenges and strategic interests demand collaborative responses.
Defense ministers Richard Marles of Australia, Sjafrie Sjamsoeddin of Indonesia and Billy Joseph of PNG agreed to hold the forum annually. The leaders described the trilateral partnership as “built on mutual respect, shared interests and a collective vision for a secure and prosperous Indo-Pacific.” They emphasized that the nations’ “breadth of military engagement” fortifies cooperation among their armed forces.
They discussed opportunities to collaborate on key areas including maritime domain awareness, humanitarian assistance and disaster response, and aviation best practices.
The nations’ proximity — with PNG between Australia and Indonesia, which bridge the Indian and Pacific oceans — enables cooperation to strengthen the regional security infrastructure more than each country could accomplish alone, experts say.
The trilateral dialogue builds on recent security agreements. In October 2025, PNG and Australia signed the Pukpuk Treaty, a mutual defense pact formalizing their long-standing defense relationship. Australia and Indonesia concluded negotiations in November for their Treaty on Common Security, which commits Canberra and Jakarta to regular high-level consultations on security matters and to “identify and undertake mutually beneficial security activities.” It also compels Australia and Indonesia to consider a joint response if either comes under attack.
Meanwhile, Indonesia and PNG have deepened security ties and discussed accelerating a defense cooperation agreement, the Jakarta-based Antara news agency reported.
“Against this spectrum, it is both timely and fitting that Papua New Guinea, Australia and Indonesia meet collectively at ministerial level,” Joseph said. “This trilateral meeting allows us to deepen trust, harmonize our approaches and enhance coordination on issues that affect all of us, including border management, maritime security, humanitarian assistance and disaster responses, defense capability development and broader regional peace and stability.
“Our discussions today will lay the foundation for a stronger trilateral relationship — one built on transparency, shared responsibility and mutual benefit.”
Observers say the trilateral dialogue can link overlapping bilateral agreements for a regional framework that allows the nations to align defense strategies, capabilities and responses.
Marles lauded the “deep strategic trust between our three countries” and cited benefits for each.
For PNG, the forum signals national security support from its largest neighbors. Indonesia gains Indo-Pacific commitments for its territorial integrity. “And from an Australian perspective, to have our two northern neighbours around the table with us is hugely significant in terms of providing security across our northern approaches for Australia, and that goes to the very heart of our nation and the very security of our continent,” Marles stated.
The collaboration sends a message from all three participants: In an era of evolving geopolitical competition, security and prosperity depend on regional integration, trust and shared responsibility.
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