Leaders are arriving in Fiji to find the Pacific Islands Forum in turmoil, with Kiribati's withdrawal striking at regional unity.
New Zealand's Jacinda Ardern touched down in Suva on Monday night, ahead of Anthony Albanese's planned arrival on Wednesday.
The Micronesian state's exit from the 18-nation body has recast the Pacific Islands Forum (PIF) leaders summit, which many hoped would paint a new and united way forward for the blue continent.
Instead, Kiribati's exit means Pacific leaders must instead forge on without full representation, which Ms Ardern labelled "disappointing".
"Would it be preferable of course for everyone to be at the table? Absolutely," she said.
"Will it stop us continuing work in those areas that even Kiribati identify as being critical for the region? No."
Speaking from Canberra, Mr Albanese linked the forum's troubles to the previous Australian government "dropping the ball" on Pacific diplomacy.
"The Fijian prime minister has done a wonderful job in trying to bring the Pacific Island (sic) Forum together," he said.
"The decision by Kiribati has been made, but we'll continue to work constructively."
On Sunday night, TVNZ revealed the departure of Kiribati, with President Taneti Maamua believing his country and the five Micronesian nations had been sidelined.
In early 2021, Micronesian members threatened to leave PIF when their proposed candidate for PIF Secretary-General lost a tight vote to Cook Islands PM Henry Puna.
Pacific leaders wrongly believed they had brokered a truce last month during talks in Fiji that would see the return of all breakaway nations.
Veteran TVNZ Pacific reporter Barbara Dreaver labelled Kiribati's departure "absolutely devastating" and the organisation's biggest crisis of its 51-year history.
"With Kiribati not at the table, it's massive and also incredibly sad, also for the Kiribati people who deserve to be represented," she said.
The leaders summit is the first in-person gathering since 2019, and taking place amid heightened diplomatic competition in the Pacific.
Earlier this year, China completed a major sweep of the region, signing a suite of bilateral agreements.
One of those was a deal with the Solomon Islands to boost security ties, which sparked grave concern in Canberra and Wellington.
In response, the United States announced a 'Partners in the Blue Pacific' body last month, boasting support from Australia, New Zealand, Japan and the United Kingdom.
The withdrawal of Kiribati, which switched its recognition from Taiwan to Beijing in 2019, is being interpreted as a deepening of China's influence.
"Regionalism is playing such a big role," Ms Dreaver said.
"There are a lot of complex issues at play behind the scenes ... big countries are trying to gain influence and pick off individual countries one by one."
NZ officials believe Kiribati's withdrawal cannot be blamed on one issue alone, with COVID-19 hampering genuine attempts at diplomacy.
Kiribati is also experiencing a major drought, with Australia announcing $2 million of aid on Monday.
TVNZ also reports other nations will miss the PIF leaders summit.
French Polynesia has dispatched its vice president, Marshall Islands may not arrive due to legal issues, and Nauru is also absent with a COVID-19 outbreak making travel impossible.
The Cook Islands may also not travel due to local elections.
For those in attendance, climate change is top of the agenda.
Members intend to sign off on the "2050 Strategy for the Blue Pacific", a long-term vision for the region, on Thursday after a full day of the leaders' retreat.
Foreign Minister Penny Wong is already in Suva ahead of Mr Albanese's arrival.
