Brazil's President Jair Bolsonaro says he wants French President Emmanuel Macron to retract "insults" against him before he considers accepting aid from the Group of Seven nations who offered US$20 million (NZ$31 million) to help fight forest fires in the Amazon.
The two leaders have become embroiled in a deeply personal and public war of words in recent days, with Bolsonaro mocking Macron's wife on Facebook and accusing the French leader of disrespecting Brazil's sovereignty.
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Macron called Bolsonaro a liar and said Brazilian women were probably ashamed of their president.
The Amazon fires have created a major crisis for the young, far-right government of Bolsonaro, who is losing popularity at home and finding himself increasingly isolated on the global stage over his response to blazes that threaten what many view as the world's key bulwark against climate change.
The issue of whether or not to accept foreign money has also become a tricky one within Bolsonaro's government, with various cabinet members taking differing stances on the offer.
Initially, as the fires gained global headlines, Bolsonaro said Brazil did not have the resources to tackle the blazes. Then, following the G7 offer, his Environment Minister Ricardo Salles called the aid "welcome".
However, on Monday evening (local time), Bolsonaro's chief of staff Onyx Lorenzoni said Brazil would reject the G7 offer although his office said that was his personal view.
Speaking to reporters in Brasilia on Tuesday, Bolsonaro said: "First of all, Macron has to withdraw his insults. He called me a liar. Before we talk or accept anything from France... he must withdraw these words then we can talk," Bolsonaro said.
"First he withdraws, then offers (aid), then I will answer."
The French president's office declined to comment.
In a later meeting with governors from Amazon states on Tuesday, Bolsonaro said his government appreciates the environmental work of the G7 nations.
However, in a boost for the Brazilian leader, US President Donald Trump on Tuesday tweeted his support for Bolsonaro, an ideological peer on issues such as the environment, China and trade.
Bolsonaro "is working very hard on the Amazon fires and in all respects doing a great job for the people of Brazil - Not easy. He and his country have the full and complete support of the USA!" Trump tweeted.
Macron made the offer of financial aid at the G7 summit in the southern French town of Biarritz on Monday after leaders had discussed the fires ravaging the world's largest tropical rainforest, often dubbed "the lungs of the world".
The number of blazes recorded across the Brazilian Amazon has risen 79 per cent this year through August 25, according to Brazil's space research agency.
The fires are not limited to Brazil, with at least 10,000 square kilometres burning in Bolivia, near its border with Paraguay and Brazil.
But Brazil is at the epicentre of the blazes, which Bolsonaro has blamed on environmentalists, non-government organisations and the weather. He has also said fires in the Amazon were more prevalent under previous left-wing governments.