The deal was set to see the two nations commit to defending each other from armed attacks as they face "emerging threats" to their security, according to a copy seen by AFP.

It was expected to be signed by leaders Anthony Albanese and James Marape on Wednesday in Port Moresby.

But the two sides instead said the signing would take place "following Cabinet processes in both countries".

The joint communique did not detail the reason for the delay, although Albanese previously said the approval by the Papua New Guinean cabinet due Monday had been delayed by the country's independence celebrations.

The two sides agreed to "strengthening and expanding defence cooperation through enhanced capability, interoperability and integration", the statement said.

And the treaty will ensure that "any activities, agreements or arrangements with third parties would not compromise the ability of either of the Parties to implement the Treaty" -- a nod to China's growing influence in the Pacific.

The agreement, which also enables the nations' citizens to serve in each other's militaries, came 50 years after Papua New Guinea gained independence from Australia.

Canberra has stepped up its engagement with the Pacific 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.

But the agreement 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.