China urges Papua New Guinea not to exclude other countries after it signed 'Pukpuk' communique with Australia

China has urged Papua New Guinea not to sign any deal that might exclude or restrict third parties from cooperating with the Pacific nation, as Australia scrambles to clinch a landmark defence treaty.

In a social media post, the Chinese embassy in PNG advised the country not to compromise its independence, urging PNG to "properly handle issues bearing on its sovereignty and long-term interests".

China is one of PNG's most important trade and economic partners, with defence experts in the island nation raising concerns the high-level pact with Australia could put strain on the country's relationship with Beijing.

The post is the most pointed public response from China to the treaty since the ABC revealed details about the pact this week.

If signed, the Pukpuk Treaty, as it is known, would see Australia and PNG become formal military allies and commit to defending each other in the event of a military attack.

It also promises that any activities either country undertakes with third parties shall not compromise the purposes of the treaty.

The document was expected to be signed on Wednesday, but it failed to get over the line, with Australia and PNG resorting to signing a communique in lieu of the actual document.

Prime Minister Anthony Albanese told journalists the deal wasn't signed this week because PNG's national cabinet couldn't reach quorum when it met on Monday to pass the treaty, because ministers were out of town for independence celebrations.

Leaders said they expected the final document to be inked in the coming weeks.

In its social media post, the Chinese embassy said it respected PNG's right to conclude a bilateral treaty with other countries, but added that such a deal should not be exclusive in nature.

"Nor should it restrict or prevents [sic] a sovereign country from cooperating with a third party for any reason. It should also refrain from targeting any third party or undermining its legitimate rights and interests," the post read.

This week, PNG Prime Minister James Marape indicated the country's defence minister, Billy Joseph, would hold discussions with China and its direct neighbour, Indonesia, regarding the proposed treaty's parameters.

The ABC has reached out to the Indonesian government for a response, but its Ministry of Foreign Affairs declined to comment.

Michael Kabuni, a Papua New Guinean political science scholar at the Australian National University, has also questioned how the treaty serves PNG, in a blog post published by ANU's Development Policy Centre.

It said PNG had more pressing priorities than increasing the combat readiness of armed forces and possibly committing them to combat outside the country.

"What PNG needs are coastguard-style capabilities: maritime patrols, satellite monitoring, fisheries enforcement, customs and border policing, engineering units and disaster response teams," Mr Kabuni wrote.

"Similar investments are required for land-border control, while tribal conflict and criminality are best addressed by expanding and equipping the police and procuring the latest technology."

It also warned that additional investment in defence forces could help to destabilise the country, pointing to Fiji as an example where " a disproportionately resourced military can become a political threat".

The piece also highlighted concerns that social obligations to tribes or clans could lead to weapons meant for the army ending up in "tribal conflicts, leading to violence that could escalate beyond the state's control".