Members of Papua New Guinea's parliament have delayed the Prime Minister's Sunday voting deadline on Bougainville's independence.

On the brink of statehood, the verdict on the autonomous region's future could now be several months away.

PNG Prime Minister James Marape back in June proposed a scheduled vote on the sovereignty of Bougainville, which holds special constitutional status within the country, amid a special sessional order on August 30.

But 111 of the 118 MPs present in the last session of this month's parliament told the speaker of the house collectively they could not come to a decision without having a parliamentary procedure.

The national parliament adjourned after much debate on Thursday while a delegation representing Bougainville's autonomous government sat observing from the gallery.

PNG's constitution and the Bougainville Peace Agreement require parliament to make the final decision, but do not spell out a procedure for how parliament may deliberate and vote on the region's overwhelmingly pro-indepedence 2019 referendum result.

There also remains a dispute over the required majority to grant Bougainville independence.

The PNG government's position was that either at least two-thirds or even three-quarter absolute majority is required, but the autonomous Bougainville government has argued for a clear 60-seat majority.

The People's Action for National Unity coalition government that includes 50 Pangu Pati MPs and 34 smaller party MPs or independents have asked for 89 MPs to ratify the 97.7 percent result in the region's non-binding referendum whose independence has been pushed back over the past seven years.

The consultation and parliamentary process has also taken much longer than expected after the joint consultation report and the agreed Melanesian Framework was just brought before parliament.

PNG's opposition leader, James Nomane, pointed out MPs could not be expected to make informed decisions when they had only just received these documents this past week.

"I ask that the government be very, very clear about when this vote will take place, and make all effort to inform all leaders of the house about: yes, what happens; no, what happens?" he said.

While the referendum result and the transition framework were tabled in PNG's parliament, Mr Marape has reportedly now conceded the final ratification vote will be pushed back to October at the earliest.

Mr Marape had urged the country to appreciate the gravity of the decision ahead of the last week of parliamentary debate.

He also cautioned MPs not to create division over the issue through threats, fear, regionalism or hostility.

"The referendum was legitimate, peaceful and overwhelming in its result, and we respect the voice expressed by the people of Bougainville," Mr Marape said.

PNG's MPs, that include four members representing Bougainville, would be voting in adherence with the 2001 Bougainville Peace Agreement, which was signed following the region's decade-long civil war that ended around three years earlier.

Bougainville Regional seat MP, Peter Tsiamalili Jr, was the sole member from the autonomous region in parliament that spoke during Thursday's final debate.

"It is also at this juncture that I also want to amplify that how fitting are we able to then bring all this journey of both sides of the house, or both sides of our regions and our islands together, all culminating back into this respectful, honourable house, a house of Melanesia," he said.

Mr Tsiamalili Jr also asked for dialogue as PNG along with Bougainville navigated a way forward that speaks "right to the heart of the Melanesian way of deconflicting".

"We must continue to have dialogue, and that peace will be found, and solutions will be found through constant dialogue," he added.

Minister for Bougainville Affairs, Manasseh Makiba, who tabled the referendum result, noted that the Melanesian Framework provided for a structured pathway and orderly transition to assume greater powers for the region in the event of an affirmative parliamentary vote.

"At the heart of the framework is concept of a transitional phase that is being termed as self-government," he said.

"Under the Melanesian Framework, an affirmative decision by the national parliament would not result in the immediate independence of Bougainville."

The autonomous Bougainville government has already said it plans to declare its own unilateral sovereignty come 2030 whether the PNG parliament further delays its independence.