Donald Trump says that Brazilian president Jair Bolsonaro has the full support of the United States and is "working very hard" to put out wildfires raging in the Amazon, even as the South American president has signalled his intention to reject $22 million in international aid for the efforts unless French president Emmanuel Macron retracts his "insults".

In a tweet, Mr Trump also praised Mr Bolsonaro's work as president to say he is "doing a great job for the people of Brazil", in spite of mounting evidence from leaked documents and scientists that the fires raging across the forest responsible for around 20 per cent of the world's oxygen supply is a result of aggressive deforestation policies pursued by the Brazilian leader.

"I have gotten to know [Mr Bolsonaro] well in our dealings with Brazil. He is working very hard on the Amazon fires and in all respects doing a great job for the people of Brazil — Not easy," Mr Trump wrote. "He and his country have the full and complete support of the USA!"

The tweet came just hours after Mr Bolsonaro signalled his intention to reject a $22 million aid package offered by G7 countries to help the fire fighting efforts.

"First of all, Mr Macron must retract the insults he gave me. First, he called me a liar. Then, the information I had is that our sovereignty is up for grabs in the Amazon," Mr Bolsonaro told reporters on Tuesday. "So, before talking or accepting anything that comes out of France's best possible intentions, he will have to take those words out and then we can talk."

Amazon rainforest swept by fires: In pictures Show all 25 1 /25 Amazon rainforest swept by fires: In pictures Amazon rainforest swept by fires: In pictures Fire rages in the Amazon rainforest in the Brazilian state of Rondonina on August 23 Reuters Amazon rainforest swept by fires: In pictures Smoke billlows from burning tracts of the Amazon rainforest in the Brazilian state of Para on August 23 AFP/Getty Amazon rainforest swept by fires: In pictures Fire rages in the Amazon rainforest in the Brazilian state of Rondonina on August 23 EPA Amazon rainforest swept by fires: In pictures Land in the Amazon rainforest left scorched in the fires in the Brazilian state of Rondonina on August 23 AFP/Getty Amazon rainforest swept by fires: In pictures Smoke billows during a fire in an area of the Amazon rainforest in the state of Rondonia, Brazil on August 23 AFP Amazon rainforest swept by fires: In pictures Fire tears through a farm in the Brazilian state of Mato Grosso AP Amazon rainforest swept by fires: In pictures An area of the Amazon rainforest left scorched in the fires in the Brazilian state of Amazonas on August 24 AFP/Getty Amazon rainforest swept by fires: In pictures Satellite images show a series of fires in the southwest Brazilian state of Rondonia on August 15 AP Amazon rainforest swept by fires: In pictures Smoke billows during a fire in an area of the Amazon rainforest in the state of Rondonia, Brazil Reuters Amazon rainforest swept by fires: In pictures A satellite image released by NASA shows the active fires that have been detected in the Amazon region EPA Amazon rainforest swept by fires: In pictures Smoke billows during a fire in an area of the Amazon rainforest in the state of Amazonas, Brazil Reuters Amazon rainforest swept by fires: In pictures Smoke billows during a fire in an area of the Amazon rainforest in the state of Rondonia, Brazil Reuters Amazon rainforest swept by fires: In pictures Smoke billows during a fire in an area of the Amazon rainforest in the state of Rondonia, Brazil Reuters Amazon rainforest swept by fires: In pictures Smoke billows during a fire in an area of the Amazon rainforest in the state of Amazonas, Brazil Reuters Amazon rainforest swept by fires: In pictures Indigenous people from the Mura tribe wallk in a deforested area inside the Amazon rainforest in the Brazilian state of Amazonas on August 20 Reuters Amazon rainforest swept by fires: In pictures Fire tears through a farm in the Brazilian state of Mato Grosso AP Amazon rainforest swept by fires: In pictures Smoke billows from a stretch of fire in the Amazon rainforest in the Brazilian state of Rondonia on 23 August AFP/Getty Amazon rainforest swept by fires: In pictures Smoke billows during a fire in an area of the Amazon rainforest in the state of Amazonas, Brazil Reuters Amazon rainforest swept by fires: In pictures Indigenous people from the Mura tribe wallk in a deforested area inside the Amazon rainforest in the Brazilian state of Amazonas on August 20 Reuters Amazon rainforest swept by fires: In pictures Smoke billows from a stretch of fire in the Amazon rainforest in the Brazilian state of Rondonia on 23 August AFP/Getty Amazon rainforest swept by fires: In pictures A view of logs felled illegally in the Amazon rainforest are seen in sawmills in the Brazilian state of Amazonas on August 22 Reuters Amazon rainforest swept by fires: In pictures A scorched patch of land in the state of Mato Grosso in Brazil on 20 August EPA Amazon rainforest swept by fires: In pictures Several fires are seen burning in the Amazon rainforest in this satellite image taken by NASA on 11 August AFP/Getty Amazon rainforest swept by fires: In pictures Smoke billows from a stretch of fire in the Amazon rainforest in the Brazilian state of Rondonia on 23 August AFP/Getty Amazon rainforest swept by fires: In pictures The sunsets behind clouds and smoke from fires in the Amazon rainforest in the Brazilian state of Rondonia on 18 August EPA

Mr Macron and Mr Bolsonaro have engaged in what has become a deeply personal war of words in recent days, with the insults amounting to what some consider to be the worst diplomatic crisis between the two countries in 40 years.

The Brazilian government had initially said it would reject an aid package, saying that "maybe those resources are more relevant to reforest Europe", and criticising France for its recent fire at the Paris cathedral Notre Dame.

But, the crisis between the two has only deepened from there, after Mr Bolsonaro liked a post on his Facebook page in which a supporter compared the appearance of Mr Macron's wife Brigitte to that of Mr Bolsonaro's, Michelle. The supporter implied in the post that Ms Bolsonaro is more attractive.

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"Don't humiliate the guy... haha," Mr Bolsonaro wrote.

In response, Mr Macron told reporters at the G7 summit in Biarritz that he saw the comments as sad for the Brazilian president and his people.

"He has made some extraordinarily rude comments about my wife," he said. "What can I tell you? It's sad. It's sad for him, and for Brazilians. I think that Brazilian women are probably ashamed to read that their president has done that."

“I think that Brazilians, a great people, are a bit ashamed of this behaviour,” the French president added. “As I have a lot of friendship and respect for the Brazilian people, I hope that they will quickly have a president who is up to the job.”

The number of fires in the Amazon has risen by 79 per cent this year, according to Brazil's space research agency. And, while Brazil is at the epicentre of the blazes, there are some 10,000 square kilometres (around 38,000 square miles) of rainforest burning in Bolivia as well, near its borer with Paraguay and Brazil.

Mr Bolsonaro has blamed the fires on environmentalists, non-governmental organisations, and on the weather. He has also sought to divert attention to past fires, during left-wing governments in his country.