Australian Prime Minister Scott Morrison will head to the island nations of Vanuatu and Fiji this week in a landmark trip aimed at mending fences and offsetting China's growing influence in the South Pacific.

Morrison on Wednesday will become the first Australian leader in decades to visit Vanuatu and the first ever to head to Fiji, where he is due to deliver a major speech on Friday.

The trip will be "focused on our security, economic and cultural partnerships," Anne Ruston, a junior minister responsible for international development and the Pacific, told AFP news agency.

Australia is by far the biggest trade partner and donor in the Pacific, but its influence has waned as Beijing has extended its reach.

Jenny Hayward-Jones, an analyst at the Lowy Institute, said there was a "sense of panic in Canberra that China's growing influence in the region is now threatening Australian interests."

Morrison has committed to send more Australian diplomats to the Pacific, increase investment and security cooperation and develop a military base in Papua New Guinea.

Australia announced in November it would offer Pacific countries up to $2bn in grants and cheap loans for telecommunications, energy, transport and water projects. At the same time, Canberra said it would beef up defence and security ties with Pacific Islands through new joint exercises and training.

In Vanuatu, local media reported that Morrison would open an Australian-backed police training college.

"We are having greater cooperation on police matters," the Daily Post quoted Foreign Minister Ralph Regenvanu as saying.

Rising China

Home to just over a quarter of a million people, the tiny chain of islands has become an unlikely geopolitical and security hotspot.

Officials from Australia and the United States believe Chinese construction and investment on Vanuatu includes plans for an eventual military base that could dramatically alter the balance of power in the region.

Pacific leaders are likely to try and leverage that rivalry to gain concessions and investment.

But Morrison's trip has been made more difficult against the backdrop of testy relations between Australia and the Pacific Islands, amid disputes over governance and climate change.

His government, facing an election in May, has downplayed the implementation of climate targets and refused to curb the extraction of coal, while many Pacific Islands see rising sea levels and intensified weather systems as an existential threat and want firm action on climate change.

A recent decision to unilaterally cancel the Australian citizenship of suspected Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group operative Neil Prakash on the grounds that he also held Fijian nationality through his father has also added to tensions with Fiji.

The archipelago denies Prakash is a citizen.

Fiji's Prime Minister Frank Bainimarama, who had been criticised for his involvement in a coup but recently won the election, has played down talk of a rift.

He described meeting Morrison in Sydney last year as a "pleasure", adding, "I look forward to seeing him again here in Fiji this week."

"As the first-ever bilateral visit by an Aussie PM, this will mark an historic step up in our diplomatic relationship," he tweeted.

Morrison's trip follows Chinese President Xi Jinping's meeting in November with eight Pacific Island leaders before the APEC summit in Papua New Guinea.

China has spent $1.32bn on concessional loans and gifts since 2011 in the Pacific region.