Tuvalu and Fiji are hosting the event in October as part of an Australian-negotiated compromise after its failed bid to host COP31, the latest edition of the world's biggest annual climate change talks.
In trilateral talks with Australia at the Pacific Islands Forum summit in Palau, Fiji Foreign Minister Sakiasi Ditoka gave a roll call of attendees secured to date.
Mr Dikota said an unspecified number of Pacific leaders would travel, as well as leaders from Antigua and Barbuda, Cape Verde, Thailand, Maldives and East Timor.
Speaking from Palau, Australian Prime Minister Anthony Albanese added his name to the list of confirmed attendees.
Additionally, "ministerial-level representation" from several countries was confirmed.
Ministers from Germany, which hosts the international climate body's secretariat, Mexico and South Korea will attend.
It follows weeks of speculation about the success of the four-day October event, which could cost the Australian government more than $19 million in event management and broadcast fees.
Challenged as to whether the short list of named attendees would represent success, Mr Bowen said the event was traditionally not designed to attract leaders.
"There will be around 3000 to 4000 attendees," he said in Palau.
"We have more than 120 international journalists already registered to attend."
Mr Albanese added critics needed to "have some respect for the process ... and Pacific leaders".
"There isn't one leader here (at the Pacific Islands Forum) who has criticised Australia for our support of bringing the pre-COP to the Pacific.
"In fact, it is the opposite."
Tuvalu is happy with the interest levels, with Prime Minister Feleti Teo saying his nation is "very grateful" for the chance to host.
"We've been advocating and trying to describe through our limited English vocabulary what the situation on the ground is like," he said.
"This is the opportunity for leaders who can make it to see for themselves the extent of our vulnerability to climate change."
In 2023, Australia and Tuvalu agreed on a world-first climate compact that affords Tuvaluans the right to emigrate to Australia given the growing existential threat.
Tuvalu is the world's lowest-lying nation, a collection of reef islands and atolls north of Fiji which is home to about 10,000 people and just two hotels.
"We've presented two options for the event in Tuvalu: one is for those that are game enough to come and spend the night over there, and the rest will come on a day trip," Mr Teo said.
"Either way, the whole nation is ready and prepared."
Mr Bowen acknowledged the logistical difficulties of a trip to Tuvalu.
"It is the least-visited country in the world," he said.
Fiji has also asked not to be judged on attendance at the summit in the remote region, but instead on whether it "advances substantive progress towards successful outcomes at COP31".
The federal opposition has lashed the event as an "overseas talkfest" that could cost up to $150 million.
On a bustling day of diplomacy at the Pacific Islands Forum leaders meeting, climate change was central to many sessions.
Alongside Mr Albanese, Palau President Surangel Whipps launched a prospectus of projects to drive the region towards 100 per cent renewable energy.
The initiative is likely to be one of the centrepieces of Mr Whipps' leadership of the forum over the next year.
"It details priority projects and country pipelines to capture progress and the necessary next steps ... the ultimate success of the prospectus effort will be measured in dollars, deals and decarbonisation," Mr Whipps said.
The effort to step up renewables, already under way, has been given a nudge by soaring fuel prices owing to the US-Iran war.
