Uncertainty surrounds Australia's latest aid mission to Tonga, after almost two dozen personnel on a Navy ship carrying humanitarian supplies to the country tested positive to COVID-19. 

Australia and several other countries are sending crucial supplies to Tonga in the wake of last week's huge volcanic eruption and tsunami, but the Pacific Island nation is determined to remain COVID-free and has insisted that all donors deliver aid without any person-to-person contact. 

Australia has already sent supplies to Tonga on military transport planes, but HMAS Adelaide is carrying larger quantities of aid, including engineering equipment, water and shelter.

Defence Minister Peter Dutton said 23 people on board the ship had tested positive to COVID-19, and Australia was consulting the Tongan authorities about what to do next.

He said while Australia was already planning to deliver the aid without any human contact, Tongan authorities were trying to balance humanitarian needs with public health concerns.

"They need the aid desperately but they don't want the risk of COVID," Mr Dutton told Sky News. 

"We will work through all of that as quickly as we can."

HMAS Adelaide is due to arrive in Tonga early tomorrow morning.

It carries Chinook helicopters which would be able to deliver the aid and return to the ship without Australian naval personnel meeting people on the ground. 

But Mr Dutton said it was too early to say if Tonga would give the green light to proceed as planned.

"Ultimately we are in the hands of the Tongan government," he told reporters. 

"Our ship will either stand off or it can port and offload the equipment there. We can do that in a contactless way and spray the equipment so the chance of passing on the virus is obviously negligible.

"So there are different options we are working through at the moment.

Last week, the Australian Defence Force turned back an aid flight to Tonga after a crew member tested positive to COVID-19, placing the supplies on a later flight instead.

The HMAS Adelaide personnel tested positive despite a screening process for crew which saw them take two COVID-19 tests last week. 

Mr Dutton said none of those infected were seriously ill, and the situation on HMAS Adelaide was comparable to that in many other Australian workplaces during the current wave of infections. 

"I'm advised that so far the cases ... are at the lower end [of severity]," he said.

The Lowy Institute's Pacific Islands Program director, Jonathan Pryke, said Tongan authorities were likely to be particularly anxious about the risk of COVID entering the kingdom.

Several other Pacific nations — including Solomon Islands, Samoa and Kiribati — which had remained largely free of the disease, are now struggling to keep out Omicron. 

"Tonga is right to take every precaution to prevent the same from happening to them — Pacific nations have traditionally been hit disproportionately hard by disease brought from outside," he said. 

"Tonga's health system would struggle under the strain of an Omicron outbreak, just like Australia's has."

Mr Pryke said HMAS Adelaide and crew were in a "tough but foreseeable position." 

"With 4 per cent of the crew COVID-positive, it's hard to see the outbreak onboard stopping," Mr Pryke said.

"If Tonga insists on HMAS Adelaide being COVID-free before they can deploy relief, they could be at anchor for weeks, raising questions about crew welfare and operability.

"The government insists aid can be delivered without contact — and it would be a terrible shame if [HMAS] Adelaide had to turn around.

"The Tongan government is facing a very difficult decision and competing risks of short-term recovery and long-term health security."

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