The historically close Pacific nations said in a joint statement they were committed to negotiating the treaty to deepen integration of their forces and make it easier to offer security support.

"This will enable our two defence forces to walk down a pathway of increasing integration and increasing interoperability," Australian Defence Minister Richard Marles said.

"We live in a world which is increasingly strategically complex," he told reporters at a press conference with his Papua New Guinea counterpart.

"It is really important that we are working with our closest friends, but in this case, we are working with family and that is very much how we see our relationship with Papua New Guinea."

Few details were given on the future treaty, which would build on an overarching security agreement signed between the two countries in 2023.

Papua New Guinea Defence Minister Billy Joseph said the treaty was important "with the geopolitics and all the different contests that are going on".

"We have consciously made a decision to choose who should be our friends as far as security is concerned," he said.

Papua New Guinea has many friends but it counts Australia as "very close", Joseph said.

Perched less than 200 kilometres (124 miles) from Australia's northernmost border, Papua New Guinea is the largest and most populous state in Melanesia.

Australia has been signing security deals, dishing out aid funding and ramping up diplomatic visits to cement its influence in the South Pacific, while China renews its efforts to woo island nations in the region.

Over the past decade, China has committed billions of dollars to Pacific nations, 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 recent years in favour of China.