Anthony Albanese and Tuvalu's Feleti Teo will announce a trailblazing treaty, the Falepili Union. (AAP Image/ Lukas Coch)

Australia and Tuvalu will announce their trailblazing treaty, the Falepili Union, has entered into force on the sidelines of the Pacific Islands Forum Leaders Meeting in Tonga.

Anthony Albanese and Feleti Teo will hold a press conference on Wednesday to mark the occasion, the Tuvalu prime minister confirmed to AAP.

“Yes, we have indicated on both sides readiness to ratify that,” he said.

“It’s a groundbreaking arrangement in terms of foreign relations.”

Mr Albanese shocked the Pacific by announcing the treaty at the 2023 PIF summit in the Cook Islands.

It is a comprehensive pact between the region’s powerhouse and the tiny Polynesian state, which is the world’s lowest nation and severely threatened by climate change.

Australia will offer up to 280 visas to Tuvaluans each year to build lives in Australia, fund climate adaptation and development projects.

Australia also gives a security guarantee, and with it, effective sign-off on any defence or security related matters in Tuvalu.

“We will have a country that will be legally committed to come to the aid of Tuvalu when Tuvalu encounters a major national disaster or a major health pandemic, and also providing security guarantees,” Mr Teo said.

The pact has been criticised by some as neo-colonisation, or blunting Tuvalu’s sovereignty.

Mr Albanese counters those concerns by saying it was negotiated and signed at Tuvalu’s request.

“We recognise the climate crisis is the single greatest threat to the livelihoods, security and wellbeing of people in the Pacific,” he said in Rarotonga in 2023.

“We have listened to the needs of our Pacific neighbours and are committed to addressing shared challenges in partnership with Forum members.”

The migration pathway means that theoretically all Tuvaluans could have moved to Australia by mid-century – as the effects of climate change begin to challenge life for the 10,000-strong nation.

“I think most of the people in Tuvalu will stay,” Mr Teo said.

“For Tuvaluans that do live in Australia, at least they have the opportunity to benefit from whatever the Australian system and government offer their permanent residents.”

Wednesday is Mr Albanese’s first full day in Nuku’alofa, having skipped the opening days of the PIF summit.

He greeted Pacific leaders warmly on arrival for the leaders plenary session, including a shoulder massage of Sitiveni Rabuka that took the Fiji Prime Minister by surprise.

Mr Albanese arrives to crunch talks on the future of New Caledonia, which has quelled deadly unrest but remains at a political crossroads.

That challenging discussion is being saved for the retreat on Thursday, when leaders will fly north to the Tongan island of Vava’u for an all-day private hideaway.

At that meeting, Tuvalu will seek support from leaders for a clause in the summit communique which decries sea level rise.

“Sea level rise is the most severe manifestation of climate change, and we need to tackle that front on,” Mr Teo said, saying he had Australia’s in-principle support.

“I’m hoping that during the during the retreat we’ll be able to persuade the other foreign leaders to support a strong statement coming out of Tonga specifically on sea level rise.”