It may come down to a crunch meeting between Australia's climate minister and his Turkish counterpart, Murat Kurum.
A deadlock between the two aspirants must be broken at this week's COP30 conference.
Ahead of last-minute negotiations, where Australia is expected to offer concessions for Turkey to drop out, Mr Bowen struck an optimistic note in a series of remarks to summit attendees.
"We are in it and we are in it to win it, let me make it clear," he said.
"We're not going anywhere and South Australia's not going anywhere."
In his first day in Belem, the Amazon rainforest gateway city, Mr Bowen gave Australia's national address, backed a Pacific decarbonisation plan, and held bilateral talks with a number of nations.
For most nations at the 2025 COP, the main game is making progress towards the Paris Agreement - a global pact that aims to limit global warming to 1.5C.
UN climate chief Simon Stiell said participants, representing much of the world but not the boycotting United States, had made major strides in negotiations.
"Nations have mustered a trillion-dollar charge into clean energy and grids, rallied around a global plan to quadruple sustainable fuels, unlocked new waves of green industry and started preparing a pipeline for new adaptation investment," he said.
Australia is engaged in those negotiations, but is otherwise preoccupied by its bid for next year's conference, which it hopes to host in South Australia in tandem with the Pacific.
Hosting decisions are made by consensus, meaning Australia needs to convince Turkey to drop its bid to avoid a diplomatic disaster and miss out.
"I don't know what the result will be. It might be a good one. It might be one that we're disappointed here, but we're fighting hard and we're going to fight hard for the end," Mr Bowen said.
Showing the dysfunction behind 2026 hosting rights, African nations have already resolved the question for the 2027 event, which is heading to Ethiopia.
In his national address, Mr Bowen spruiked Australia's climate credentials, including a 2035 emissions target of 62-70 per cent below 2005 levels.
Pacific leaders have unanimously endorsed the bid for some time, with Vanuatu Climate Minister Ralph Regenvanu saying the region was backing it, but he "didn't have any sense" of the outcome.
"Pacific small island developing states are meeting delegations about it too," he told AAP from Belem.
Australia has an overwhelming majority of support of the group that decides the outcome.
A briefing note seen by AAP states Australia has the explicit backing of 24 of the 28 "Western European and Others Group" nations, while Turkey has no publicly declared supporters.
While questions are being asked of the large cost of hosting the event, climate advocacy groups are desperate for the government to pull it off.
"This is a once-in-a-generation chance and will be a missed opportunity if they don't win the COP presidency," Australian Conservation Foundation climate manager Gavan McFadzean told AAP.
"Our Pacific neighbours have contributed the least to climate crisis, but are amongst the worst affected, and there's an enormous economic and jobs opportunity to ... transition our coal and gas exports to renewable energy based manufacturing."
Mr Bowen also supported a report into Pacific decarbonisation, backed by Vanuatu, Tuvalu, Australia's Smart Energy Council and others.
Pacific nations are plagued by unreliable or expensive power sources, such as imported diesel, and are seeking to transition away.
"If we can manage the rapid transition of our energy systems in Pacific Islands, it can be a beacon for the rest of the globe," Mr Regenvanu said.
"Our survival depends on it."
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