The pact -- seen as an attempt to counter Beijing's rising Pacific influence -- is expected to be signed by leaders Anthony Albanese and James Marape on Wednesday in Port Moresby.

It comes as the Pacific nation celebrates 50 years of independence from Australia.

"Each Party recognises that an armed attack on either of the Parties within the Pacific would be dangerous to each other's peace and security and the security of the Pacific," it states.

Both parties, it adds, declare they will "act to meet the common danger, in accordance with its constitutional processes."

Australia and Papua New Guinea are facing "emerging threats to their national interests and regional security", it reads.

They are "resolute in working together to support a peaceful, stable, prosperous region that is respectful of sovereignty," it adds.

The deal also enables nationals from the two countries to serve in each other's militaries.

The agreement follows an overarching security agreement signed between the two countries in 2023.

- Celebrations delay deal -

Widely expected to be signed off by the Papua New Guinean cabinet on Monday, Albanese told media that had been postponed due to the independence celebrations.

"They didn't have quorum, because everyone's gone back to their places where they're from, to celebrate this as a celebration throughout the entire nation," he told media in the capital Port Moresby.

"We will be able to advance the treaty tomorrow," Albanese added.

To the north of Australia, Papua New Guinea is the largest and most populous state in Melanesia.

China has committed billions of dollars to Pacific nations over the past decade, funding hospitals, sports stadiums, roads and other public works.

It is an approach that appears to be paying dividends.

Solomon Islands, Kiribati and Nauru have all severed diplomatic ties with Taiwan in favour of China in recent years.

Canberra has stepped up its engagement with the region in a bid to counter Beijing's influence.

Albanese was in Vanuatu last week to discuss a deal aimed at deepening Australia's links to the Pacific nation.

However, the deal was not signed, with Prime Minister Jotham Napat citing concerns that its wording would limit Vanuatu's ability to access funds for "critical infrastructure" from other nations.