The UK will not contribute to a flagship fund for the world’s remaining tropical forests, in a bitter blow to the Brazilian hosts on the eve of the Cop30 climate summit.

Keir Starmer flew to Belém, at the mouth of the Amazon, on Wednesday to join the summit of world leaders hosted by Brazil’s president, Lula da Silva.

The key announcement for Brazil at the leaders’ summit on Thursday, which is taking place a few days before the start of the main Cop30 UN climate summit, will be the Tropical Forests Forever Facility (TFFF).

This fund aims to raise $125bn for governments and local communities that protect existing forests, such as the Amazon and the Congo basin. Lula hopes to raise $25bn from public sources, mainly developed countries attending Cop30, with the rest to come from the private sector and financial markets.

But he has had difficulty persuading cash-strapped governments, many of which are already cutting their aid budgets, to provide money. Under Joe Biden, the US was seen as a possible contributor, but with Donald Trump as president that will not happen.

The UK’s decision will be a major letdown, as Britain has previously played a big role in stopping deforestation. “The Brazilians are fuming,” one source told the Guardian.