French President Emmanuel Macron – who hosted a G7 summit that ended on Monday – said $22m (£18m) would be released.
But Brazilian ministers say the money is not needed and accuse foreign powers of wanting control of the Amazon.
Satellite data shows fires – mostly in the Amazon – are burning at record levels.
Commenting on the G7 offer of aid, Brazilian President Jair Bolsonaro’s chief of staff, Onyx Lorenzoni, told the Globo news website: “Thanks, but maybe those resources are more relevant to reforest Europe.
“Macron cannot even avoid a predictable fire in a church that is part of the world’s heritage, and he wants to give us lessons for our country?” Mr Lorenzoni added, in a reference to the fire that hit Notre-Dame cathedral in Paris in April.
Foreign Minister Ernesto Araujo says there are already mechanisms under the auspices of the UN climate convention to fight deforestation.
“Efforts of some political currents to extrapolate real environmental issues into a fabricated ‘crisis’ as a pretext for introducing mechanisms for external control of the Amazon are very evident,” he added in a tweet.
Mr Bolsonaro has previously said his government lacked the resources to fight the record number of fires in the Amazon.
Greenpeace France has described the G7’s response to the crisis as “inadequate given the urgency and magnitude of this environmental disaster”, it said in a statement (in French).
On Monday, actor Leonardo DiCaprio pledged $5m towards helping the rainforest.
One world expert on forestry says what is needed in Brazil is a change in political priorities.
“The funding for Brazil’s environment agency has gone down by 95% this year, it [has] essentially gutted large part of the actions that have been put in by the agricultural ministry,” Yadvinder Malhi, professor of Ecosystem Science at the University of Oxford, told the BBC’s Today programme.
“So the real thing is to look at the political direction of governance in the Amazon that’s changing under the new Brazilian government.”
What was pledged?
The $22m was announced on Monday as the leaders of the G7 – Canada, France, Germany, Italy, Japan, the UK and the US – met in Biarritz, France.
Mr Macron said the funds would be made available immediately – primarily to pay for more firefighting planes – and that France would also “offer concrete support with military in the region”.
But Mr Bolsonaro – who has been engaged in a public row with Mr Macron in recent weeks – accused the French leader of launching “unreasonable and gratuitous attacks against the Amazon region”, and “hiding his intentions behind the idea of an ‘alliance’ of G7 countries”.
Why is Mr Bolsonaro so prickly about foreign aid?
President Bolsonaro has long maintained that European countries are trying to gain access to Brazil’s natural resources. He alleges that European interest in the welfare of the Amazon is a thin guise for attempts to gain a foothold in the region.
Asked by international journalists about environmental protection of the Amazon at a press briefing on 6 July, he said: “Brazil is like a virgin that every pervert from the outside lusts for”.
He also said Europeans had “got it into their heads” that the Amazon did not belong to Brazil.
Since then, he has stressed the issue of sovereignty time and time again.
“These countries that send money here, they don’t send it out of charity,” Mr Bolsonaro said last week. “They send it with the aim of interfering with our sovereignty.”
What is Brazil doing?
On Friday, facing mounting pressure from abroad, President Bolsonaro authorised the military to help tackle the blazes.
Brazil says 44,000 soldiers have been deployed to combat the fires and environmental crimes in the Amazon, and military operations are under way in seven states as the result of requests for assistance from local governments.
Wildfires often occur in the dry season in Brazil, but satellite data published by Brazil’s space agency has shown an increase of 80% this year.
BBC analysis has also found that the record number of fires being recorded also coincides with a sharp drop off in fines being handed out for environmental violations.
As the largest rainforest in the world, the Amazon is a vital carbon store that slows down the pace of global warming. It spans a number of countries, but the majority of it falls within Brazil.