President Jair Bolsonaro has insisted that the Brazilian areas of the Amazon rainforest are sovereign territory.
Conservationists blame Mr Bolsonaro and his government for turning a blind eye to farmers and loggers clearing land in the Amazon, hastening deforestation.
But in an address at the United Nations in New York, he struck a defiant note.
He said it was a "fallacy" to describe the Amazon as the heritage of humanity and a "misconception" that its forests were the lungs of the world.
Brazil - home to more than half the Amazon rainforest - has seen a significant rise in the number of fires in 2019, according to US space agency Nasa and others.
Environmentalists say the far-right Mr Bolsonaro's policies have led to an increase in fires this year, and that he has encouraged cattle farmers and loggers to clear large areas of the rainforest since his election last October.
Speaking at the UN General Assembly, Mr Bolsonaro criticised what he described as sensational reporting in the international media.
"Using and resorting to these fallacies, certain countries, instead of helping ... behaved in a disrespectful manner and with a colonialist spirit," he said.
"They even called into question that which we hold as a most sacred value, our sovereignty."
Mr Bolsonaro was speaking the day after an impassioned speech from teenage Swedish climate campaigner Greta Thunberg, who accused world leaders of betraying young people in favour of what she described as "fairy tales of eternal economic growth".
The Brazilian president defended his government's treatment of indigenous people, saying many backed his policies.
"Some people both inside and outside Brazil... have insisted on treating and keeping our Indians as though they were real cave men," he said.
More than 800,000 indigenous people live in 450 demarcated indigenous territories across Brazil, about 12% of Brazil's total territory. Most are located in the Amazon region and some groups still live completely isolated and without outside contact.
President Bolsonaro, who took office in January, has repeatedly questioned whether these demarcated territories - which are enshrined in Brazil's constitution - should continue to exist, arguing that their size is disproportionate to the number of indigenous people living there.
His plans to open up these territories for mining, logging and agriculture are controversial.
Mr Bolsonaro's visit to New York has sparked several protests by environmentalists.
He has drawn intense domestic and international criticism for failing to protect the Amazon region, a vital carbon store that slows the pace of global warming.
The view from the 'epicentre of the crisis'
By Will Grant, BBC Latin America correspondent, Pará state
The state of Pará is often considered the epicentre of the environmental crisis in the Amazon. From above, the range of different pressures and stresses being put onto the rainforest by human activity is abundantly clear.
As our light aircraft swooped down, the scar of open land interrupting the forest canopy revealed itself to be a vast series of illegal gold mines. The runoff and slurry were so extensive that they resembled a river - but a toxic one contaminated by mercury, which seeps into the Amazon's waterways and ecosystems.
It is not just mining, either. In the part of the Amazon we visited, a recent wildfire had consumed an area of forest the size of 1,600 football pitches in just four days.
In the Amazonian town of Alter do Chão, opinion was split between those urging greater protection for the forest and those saying further development was needed to bring in jobs.
Yet everyone I spoke to agreed that the Amazon rainforest was a living, breathing resource that must be respected - and that fire, mining and large-scale agriculture were doing nothing but harm.