French President Emmanuel Macron said the two nations -- alongside fellow democracy India -- had a responsibility to protect the region from "hegemony" -- a veiled reference to Beijing's growing might.
"What's important is to preserve rules-based development in the region... and to preserve necessary balances in the region.
"It's important with this new context not to have any hegemony," he added through an interpreter.
France has a number of island territories in the Pacific Ocean.
Australia has become increasingly alarmed at China's push into the Pacific, which could potentially upset the strategic balance in the region.
Neighbour New Zealand has also voiced concerns about "strategic anxiety" -- diplomatic code for Beijing's influence among the region's island nations.
Reports last month -- which were denied -- said Beijing wanted to establish a permanent military base in Vanuatu.
Australia's Lowy Institute estimates China provided US$1.78 billion in aid, including concessional loans, to Pacific nations between 2006-16.
"A rule of law that says might is not right, that the big fish cannot eat the little fish and the little fish eat the shrimps, that is absolutely critical," he said.
"Now, that rule of law is what we seek to maintain in our region."
Macron, only the second serving French leader ever to visit Australia, has described ties between the two countries as historic, recalling how Australian soldiers helped defend France in World War I and II.
The two leaders signed a series of agreements, including a new symposium to bolster defence industry and business cooperation to build on a Aus$50 billion (US$37 billion) deal in late 2016 for France to supply Australia's new fleet of next-generation submarines.
There were also climate-based agreements on developing technologies to harness solar power and protect reefs.
Macron on Thursday heads to New Caledonia to rally support for the territory remaining part of France when residents go to a referendum in early November.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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