The United States has been ramping up efforts to re-engage in the South Pacific, where China has emerged as a rising diplomatic and military power.

Blinken's trip to Brisbane caps a diplomatic blitz in which he has also visited Tonga and New Zealand, while US Secretary of Defense Austin arrived from Papua New Guinea.

The US duo will hold high-level talks across two days with their Australian counterparts, Foreign Minister Penny Wong and Defence Minister Richard Marles.

While military cooperation is expected to dominate discussions, Washington has signalled that other issues such as climate change and supply chain security also sit high on the agenda.

The United States views Australia as a useful friend in its quest to loosen Beijing's dominance of emerging clean energy industries such as electric vehicle manufacturing.

Australia is one of the world's largest producers of lithium -- a key component of rechargeable batteries -- but currently sends most of its ore to be processed in China.

"The United States are looking at options to source critical technologies and their components from allied countries in place of China," said researcher Tom Corben from the United States Studies Centre at Sydney University.

"That applies as much to the climate as it does to defence -- given the emphasis placed on things like next-generation batteries," he told AFP.

Climate change is also emerging as a security threat in its own right as the toll from increasingly severe natural disasters mounts in Australia and the broader Pacific.

- Nailing down AUKUS -

Corben said the discussions were a chance to nail down the details of the AUKUS pact, a fledgling military pact between Australia, the United Kingdom and the United States.

Under "pillar one" of the agreement, Australia will acquire a fleet of nuclear-powered submarines -- billed as one of its biggest-ever military upgrades.

Attention now turns to "pillar two", which revolves around cyber warfare, artificial intelligence and the development of hypersonic missiles.

Another key issue likely to come up concerns efforts to shore up longstanding relationships with Pacific nations that have been aggressively courted by China.

Pentagon chief Austin comes to Australia from Port Moresby, where the US signed a defence agreement earlier this year giving troops access to key military facilities.

"It all fits into wider efforts to make US force posture in the Indo-Pacific more resilient by drastically increasing the number of locations the Chinese military have to consider," said Corben.

Washington's latest push is likely to irritate China, which has despatched a raft of its own senior officials into the Pacific backed with generous aid commitments and infrastructure loans.

Beijing has committed the lion's share of funding to the upcoming Pacific Games in Solomon Islands, and recently despatched the "Peace Ark" hospital ship to treat patients in Kiribati, Tonga, Solomon Islands and Vanuatu.