Australia and Papua New Guinea have officially signed the Pukpuk Treaty to "support each other's defence and contribute to a region that is peaceful, stable and prosperous".

The Treaty — named after the pidgin word for crocodile — was signed in Canberra on Monday by Prime Minister Anthony Albanese and PNG's Prime Minister James Marape. Mr Albanese said both nations had agreed not to undertake any activities or enter into any agreements that would compromise its implementation.

"This Treaty elevates the relationship between our two nations to the status of an alliance," Australia's Prime Minister said — Australia's first in more than 70 years, and only its third after that with the United States and New Zealand.

"This alliance of equals reflects our common commitment to a more secure and stable region. Above all, it is founded on the friendship between our peoples."

Mr Albanese said the treaty contains a mutual defence obligation — similar to the ANZUS Treaty — meaning "we declare in the event of an armed attack on either of our country, we would both act to meet the common danger".

The treaty also provides for as many as 10,000 PNG citizens to serve with the Australian Defence Force. The Australian government confirmed consultations will begin to establish a recruitment pathway, with PNG citizens who are permanent residents in Australia eligible to apply from next year.

Mr Marape thanked Mr Albanese for accepting the "proposal from our Government to enter into this Treaty" and described it as a "landmark for our two nations".

"This Treaty was not conceived out of geopolitics or any other reason," he said.

"But out of geography, history and the enduring reality of our shared neighbourhood. It is about one bigger fence that secures two houses that has its own yard space. It is in this construct that we're going about in signing this Treaty."

Mr Marape also dismissed suggestions it was linked to rugby league, saying: "I will never live to regret this choice I made."

The Australian government has faced claims it is seeking influence by supporting PNG's bid for an NRL team in 2028, but Mr Marape has consistently denied any connection.

Mr Albanese added: "This is about our relationship with Papua New Guinea, which is in the context of the work that we've done in our region."

"I've said Australian foreign policy has three pillars. The alliance with the United States is one of them, our support for regional engagement [the second], and that is something that we have stepped up the Pacific Island forum with our near neighbour, with Asia, and the third is our support for multilateralism. They've been the foundations of Australian foreign policy for a long period of time."

The signing had been delayed during PNG's 50th anniversary of independence from Australia. It will now go before both nations' parliaments for approval.

Mr Albanese had returned from those celebrations with only a joint communiqué after PNG's cabinet was unable to reach a quorum to approve the treaty.

While Australia's political parties have shown bipartisan support, some opposition members in PNG remain concerned it could distance the country from others in the region, particularly China, in light of PNG's foreign policy principle of "friends to all, enemies to none".

Asked if the treaty could draw PNG into a wider Pacific conflict, Mr Marape said leaders must consider worst-case scenarios but insisted it was a treaty of peace.

"We maintain friendships to all enemies, we advocate peace in wherever we engage in as far as foreign relations concern," he said.

He told reporters it was "not a treaty setting up enemies," but instead about both countries being "good neighbours, the closest of neighbours, now the newest of allies".

"It's about our relationship, recognising this as part of the sovereignty of other nations, and is consistent with that," he added.

Australia has recently pursued broader agreements across the Pacific, including a climate pact with Tuvalu and a migration deal with Nauru.

However, a $500 million security pact with Vanuatu was postponed last month, causing political embarrassment for the government.

Mr Albanese avoided questions on Monday about that delay and whether the treaty under negotiation with Fiji would mirror the Pukpuk Treaty, saying his focus was on PNG.