Australia and Fiji have signed an agreement to allow the operation of each nation's militaries in the other country, with ministers describing it as a significant step for security cooperation.
Pacific island nations have said climate change is the biggest security threat to the region, but tensions between superpowers China and the United States have also been felt, after the Solomon Islands struck a security pact with Beijing in April.
South Pacific defence ministers met in Tonga earlier this week, with Australia seeking a closer military relationship with the three island nations that have defence forces - Fiji, Papua New Guinea and Tonga - to counter China's security push in the region.
"Now's the time to be close to friends," Australia's defence minister Richard Marles told reporters in Fiji on Thursday, referring to a "precarious" global strategic situation and the impact of climate change.
Marles said the Status of Forces agreement signed with Fiji on Thursday, giving a legal framework for the presence of one country's forces in another, was rare for Australia and would allow a closer working relationship between the defence forces.
"It is a very, very significant step," he said.
Fiji's defence minister Inia Seruiratu said the defence forces trained and deployed together across the region, and the agreement brought "a new height of security cooperation".
"We know and understand the geopolitics of the region and the role that we play, Australia and New Zealand, and the need for us to stand united and cooperate," he told reporters.
A statement on Thursday from the South Pacific Defence Ministers Meeting, comprised of Papua New Guinea, Fiji, New Zealand, France, Chile, Australia and Tonga, said the Australian-funded Blackrock military camp in Fiji would be developed into a regional centre for disaster response.
The United States, Britain and Japan had attended the meeting as observers, a Tongan government statement said.
Tonga's Prime Minister Siaosi Sovaleni told the meeting "geopolitical complexities" and non-traditional security threats "demand that we forge enduring mutual cooperation for present and future generations", the statement said.
Australia is also negotiating a defence treaty with Papua New Guinea.
(Reporting by Kirsty Needham; Editing by Lincoln Feast.)
