French President Emmanuel Macron has said the record number of fires in the Amazon rainforest is an "international crisis" that needs to be on the top of the agenda at the G7 summit."Our house is burning," he tweeted.
Brazil's President Jair Bolsonaro responded by accusing Mr Macron of using the issue for "political gain".
He said calls to discuss the fires at the G7 summit, which Brazil is not participating in, evoke "a misplaced colonialist mindset".
The largest rainforest in the world, the Amazon is a vital carbon store that slows down the pace of global warming, reports BBC.
Satellite data published by the National Institute for Space Research (Inpe) has shown an increase of 85% this year in fires across Brazil, most of them in the Amazon region.
Conservationists have blamed Mr Bolsonaro's government for the Amazon's plight, saying that he has encouraged loggers and farmers to clear the land.Mr Bolsonaro has suggested that non-governmental organisations started the fires, but admitted he had no evidence for this claim. In comments on Thursday, he acknowledged that farmers might be involved in setting fires in the region, according to Reuters news agency.
What have the leaders said?
Mr Macron, host of this weekend's G7 summit of some of the world's most advanced economies, warned that the health of the Amazon was a matter of international concern.
"The Amazon rainforest - the lungs which produce 20% of our planet's oxygen - is on fire," he tweeted. "Members of the G7 Summit, let's discuss this emergency first order in two days!"
Mr Bolsonaro responded by accusing the French president of using a Brazilian domestic issue for "personal political gain".
He said he was open to dialogue about the fires if it was "based on objective data and mutual respect", but hit out at the calls for it to be discussed at the G7 summit.
"The French president's suggestion that Amazonian issues be discussed at the G7 without the participation of the countries of the region evokes a misplaced colonialist mindset, which does not belong in the 21st century," he wrote on social media.
UN Secretary-General Antonio Guterres has also said he is "deeply concerned" about the fires in the Amazon.
What causes the fires?
Wildfires often occur in the dry season in Brazil but they are also deliberately started in efforts to illegally deforest land for cattle ranching.
"The dry season creates the favourable conditions for the use and spread of fire, but starting a fire is the work of humans, either deliberately or by accident," Inpe researcher Alberto Setzer told Reuters news agency.
Ricardo Mello, head of the World Wide Fund for Nature (WWF) Amazon Programme, said the fires were "a consequence of the increase in deforestation seen in recent figures".