Brazil's President Jair Bolsonaro has approved a 24 per cent cut to the environment budget for 2021 from last year's level, just one day after he vowed to increase spending to fight deforestation.
Speaking on Thursday to a virtual climate summit organised by US President Joe Biden, Bolsonaro pledged to double the budget for environmental enforcement and end illegal deforestation in Brazil by 2030.
The US government applauded those targets, part of a shift in tone by the far-right leader, although many environmentalists said they would not take the rhetoric seriously before seeing real progress.
Less than 24 hours later, Bolsonaro on Friday signed off on the 2021 federal budget that included 2 billion reais ($A472m) for the Environment Ministry and agencies it oversees, down from 2.6 billion ($A613m) initially approved last year, according to the official government gazette.
Spending can be adjusted over the course of the year.
"The gesture of giving a speech yesterday isn't enough," Congressman Rodrigo Agostinho, leader of the environmental caucus, said.
"Brazil's government needs to do its homework."
Bolsonaro vetoed a list of environmental budget provisions worth 240 million reais ($A56.6m), including outlays for environmental enforcement.
Bolsonaro's office directed questions to the Economy Ministry.
The ministry said the environment budget now was in line with what the president originally proposed, and counteracted spending increases approved by Congress.
Late on Friday, Environment Minister Ricardo Salles posted on social media a request addressed to the Economy Ministry for 270 million reais ($A63.7m) in additional funding for environmental agency Ibama and parks service ICMBio.
A detailed budget listing individual expenditures has yet to be released.