"The 39 members of the Alliance of Small Island States (AOSIS) have continually expressed their concerns about the prohibitive costs associated with travelling to and staying in Belem," Ilana Seid, chair of the group and representative of Palau at the United Nations, told AFP by email.

"We do not have the luxury of large budgets at our disposal to ensure our participation," she said on behalf of the countries that dot oceans worldwide and are especially vulnerable to sea level rise and superstorms amplified by global warming.

"If our delegations are reduced or unable to participate effectively, it would be a failure in the pursuit of climate justice for those whose lives and livelihoods are on the front line of a crisis they did not cause," Seid said.

The UN climate conference will be held in November in Belem, an Amazonian city of 1.3 million inhabitants with limited hotel accommodations.

Less than 100 days before the event, the prices have caused such widespread consternation that some countries have asked for the conference to be moved to another city.

Austria's head of state this week cancelled his planned trip, citing "exceptionally high costs".

Recent months have seen hotels advertising rooms at 1,200 euros ($1,400) a night.

Some offerings on the Airbnb booking platform were even higher.

Airbnb said it was "committed to increasing efforts to raise awareness in the local hosting community and encourage responsible practices".

Since November 2023 the number of listings for the Belem region had surged to 6,100 from 1,000, "which represents around 19,000 beds", it told AFP, in a statement.

The COP30 presidency, which does not intend to move the event, has offered reduced-price accommodation for developing and island countries, including cabins on cruise ships.

But the price of these rooms is "still higher" than the package agreed for UN-backed travellers, Seid said.

"The allocation of 15 rooms per delegation is also alarming, meaning that many of our countries would be forced to reduce the size of their delegations," she said.

The COP30 president, Andre Correa do Lago, acknowledged this month that there were "extreme concerns" and that "reducing delegations is obviously not what Brazil wants because we need a very intense and productive COP".

"We are trying to find solutions to this price issue," he told journalists.

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