Fears China is mapping crucial submarine routes have intensified as hi-tech ships survey waters near a naval base undergoing upgrades.
Hi-tech Chinese ships have been detected near Manus Island as the United States and Australia begin naval base upgrades closeby.
The deployment of Chinese ships to waters near Papua New Guinea has sparked concern as experts believe any information gathered by the Chinese surveys could be crucial in any future maritime conflict with the United States, reports the ABC.
Chinese civilian ships are increasingly being deployed beyond the mostly US-aligned "Second Island Chain", sparking fears China is gathering mission planning data and mapping crucial submarine routes.
GPS satellite data reveals two Chinese research vessels mapping waters in PNG's Exclusive Economic Zone (EEZ) north of Manus Island in December last year, two weeks after US vice President Mike Pence announced the redevelopment of the Lombrum Naval Base.
The deepwater scientific surveys are part of Beijing's oceanographic research of the Western Pacific, the Chinese "Distant-Ocean Research fleet" already conducting surveys around the Philippines, Palau, Guam and Japan.
According to a December 23 report seen by the ABC, the "even spacing between legs in Papua New Guinea's EEZ indicates bathymetric data collection" taking place.
While Senior Australian and American military officials acknowledge the oceanographic surveys are entirely lawful, they are aware the civilian ships are also gathering invaluable data for future defence operations, ABC's defence Correspondent, Andrew Green, reports.
"The information gained for resource purposes has dual use for military purposes," Mr Green was told by one long-serving Australian defence official, who wished to remain anonymous.
"Establishing the baseline data around what the seabed is made out of, what the seabed terrain is like, the salinity and what thermal layers exist in the water is useful for mining but it also helps determine the acoustic conditions for submarine operations.
"International law permits the conduct of marine scientific research in international waters, within certain parameters, provided that activities do not infringe on the rights of other states or unjustifiably interfere with other legitimate uses of the sea," a spokesperson from the Australian Defence Department told the ABC.
A US Naval College report from November 2018 concludes "China's out-of-area oceanographic research activities raise a number of concerns for US policymakers".
When pressed by the publication, China's Foreign Ministry insisted its extensive oceanographic research is all conducted within international law and is inherent to global scientific development.
"China's oceanographic, scientific research in the Western Pacific is totally in line with the United Nations Convention on the Law of the Sea and made contributions to maritime scientific study," Foreign Ministry spokesman Lu Kan assured the ABC.
A Memorandum of Understanding was signed last month by Defence chiefs from Australia and PNG, a guide to the joint upgrade of the Lombrum Naval Base.
The Federal Government says the increased cooperation at the PNG Defence Force base in Manus Province is a "natural extension of our longstanding and collaborative Defence partnership".
The scale of the US commitment remains unclear, with Mr Pence refraining from revealing how much money the Trump administration would contribute to the project, or whether American vessels will be based at Lombrum permanently.