Australian taxpayers are on track to pay at least a third of the costs of Papua New Guinea's ambitious plan to host next year's APEC summit to stave off rising Chinese influence in the poverty-stricken nation.

Key points: Summit will swallow the equivalent of one-fifth of Australia's total annual aid budget to PNG

Summit will swallow the equivalent of one-fifth of Australia's total annual aid budget to PNG Government is persuaded any retreat will risk China filling the breach

Government is persuaded any retreat will risk China filling the breach "We stand by our friends when they need assistance," Michael Keenan says

Confirmation this week that 73 Australian Federal Police (AFP) officers will remain in PNG until the end of the November 2018 leaders' meeting marks the beginning of a series of commitments covering security, diplomatic support, advisory roles, intelligence services and immigration processes.

The ABC has been told the AFP commitment of $48 million together with other contributions in cash and kind will exceed $100 million before the summit is held, swallowing the equivalent of one-fifth of Australia's total annual aid budget to PNG of $558 million.

The deepening financial exposure to PNG's expensive APEC showcase has generated debate at the highest levels of the bureaucracy and across the ministry over its affordability at a time when Australia's own budget is mired in deficits for at least the next four years.

After contemplating more stringent limits or even leaving the Peter O'Neill Government to fund the event itself, the Government was persuaded by security and foreign policy advisers that any retreat would risk China filling the breach.

Asked about the risk, Justice Minister Michael Keenan acknowledged "obviously that's a possibility" but added "we are their closest security partner and I consider that is going to continue into the future".

"We stand by our friends when they need assistance — this is just another indication that Australia is a good friend," he said.

With modest hotel facilities and poor infrastructure, Port Moresby is to host the year-long programme of APEC meetings culminating in the November Leaders' Summit of Presidents and Prime Ministers from 21 countries.

Cruise and naval ships are likely to be needed to accommodate some international delegations.

PNG has set aside a total budget allocation for the summit of 800 million kina ($330 million), excluding the construction of the purpose-built APEC Haus convention centre being built by LNG producer Oil Search through a tax-credit scheme.

But PNG's national economy and the Government's budget are faltering under slow growth and high debt, raising questions there and in Australia over whether the summit with up to 10,000 visitors can be afforded.

The country is already awash with billions of dollars worth of Chinese bank loans, infrastructure projects, mines and telecommunications investments and on Prime Minister O'Neill's state visit to Beijing last year President Xi Jinping stressed his country "supports Papua New Guinea to host the 2018 APEC Economic Leaders' Meeting".

'We've historically assumed responsibility for South Pacific'

Australian Government sources have told the ABC the prospect of China bankrolling the summit loomed as a significant factor in its decision to prolong the AFP deployment and to lend other forms of support.

The Department of Foreign Affairs said those forms of support would come from "a range of Australian Government agencies, including the Attorney-General's Department, Department of Defence, Department of Foreign Affairs and Trade (DFAT), Department of Immigration and Border Protection, Department of Infrastructure and Regional Development and Treasury".

There is no official budget for Australia's financial exposure to the meetings but DFAT describes the total government venture as "providing a range of training and support to increase the Government of Papua New Guinea's ability to deliver a safe and secure APEC, particularly for major event planning, security and policy development".

Analysts, including Australian National University's Dean of the College of Asia and the Pacific Michael Wesley, believe that not providing such aid risks a souring of relations with PNG which could then court rising powers including China, as Fiji is doing with its "look north" foreign policy designed to shun Australia and New Zealand.

But Professor Wesley said allowing PNG's ambitious APEC plans to collapse would also inflict "reputational" damage on Australia.

"We have historically assumed responsibility for the South Pacific and we are still the largest provider of development assistance in the region," he said.

"If PNG took on a task like this and was seen to fail through a lack of interest and support from Australia then it would do our reputation a great deal of damage through the South Pacific and more broadly."

Since the election of Donald Trump's administration, the Australian Government is highly aware of Washington's expectation that Australia play a lead role in thwarting security risks in its neighbourhood.

Government sources have noted that any threats against the Port Moresby summit would be viewed dimly by the United States, as would the deepening of Chinese interests.