Brazil's president has signed an order deploying the military to help protect the Amazon from wildfires, a state governor in the country has said.
President Jair Bolsonaro had earlier suggested troops could be sent in to battle the fires in the face of a global outcry.
Antonio Denarium, the governor of the state of Roraima, has said the move will go ahead.
Mr Bolsonaro's office also said he will reveal firefighting plans for the Amazon on Friday and they are already being implemented.
France and Ireland threatened to block a free trade deal between the EU and a South American trading bloc earlier unless Mr Bolsonaro took action, while the British prime minister has said he will "call for a renewed focus on protecting nature" at a G7 summit.
As tensions escalated over the crisis on Friday, France accused Mr Bolsonaro of failing to respect his "commitments on the climate".
The Elysee Palace claimed in a statement that the Brazilian president had lied to France's President Emmanuel Macron over the issue.
Boris Johnson was backing Mr Macron's push for the situation to be on the agenda when G7 leaders meet in Biarritz, France, on Saturday.
Downing Street said Mr Johnson was "deeply concerned by the increase in fires in the Amazon rainforest and the impact of the tragic loss of these precious habitats".
Mr Macron has called the wildfires an international crisis and tweeted: "Our house is burning. Literally. The Amazon rainforest - the lungs which produces 20% of our planet's oxygen - is on fire."
France added that it now opposed an EU trade deal "in its current state" with the Mercosur bloc of South American nations that includes Brazil, Argentina, Paraguay and Uruguay.
Mr Bolsonaro said later on Friday that Brazil has concluded a trade deal with EFTA, the European free trade group formed by Switzerland, Norway, Iceland and Liechtenstein.
German Chancellor Angela Merkel said the wildfires were "shocking and threatening".
The number of forest fires in Brazil since January - more than 74,000 - has increased by 83% compared with the same period last year, with smoke that is visible from 400 miles up in space.
World leaders are increasingly worried about the situation, as the Amazon - described as the world's lungs - is a vital absorber of carbon dioxide from the atmosphere.
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Just eight months into his presidency, Mr Bolsonaro has made it clear he wants to open the Amazon up to the demands of mining, agricultural and logging companies.
Labour leader Jeremy Corbyn said Mr Bolsonaro had "allowed and indeed encouraged these fires to take place".
Irish Prime Minister Leo Varadakar said: "There is no way that Ireland will vote for the EU-Mercosur free trade agreement if Brazil does not honour its environmental commitments."
Finnish prime minister Antti Rinne also expressed concern, saying he is "truly worried about the attitude Brazil seems to have adopted right now regarding" fires in the Amazon.
The Brazilian leader has hit back at his critics and accused Mr Macron on Twitter of using a "sensationalist tone" that "does nothing to solve the problem".
He later suggested the military might help to tackle the rainforest fires but did not say when.
Brazilian army general Edson Leal Pujol has said the military is "ready" to defend the Amazon rainforest from wildfires.
Mr Bolsonaro has previously described rainforest protections as an obstacle to economic development, sparring with critics who note the Amazon produces vast amounts of oxygen for the planet.
The Brazilian leader said he wants to convert land for cattle pastures and soybean farms.
He said other countries' concerns over the widespread blazes revealed a "colonialist mindset".
Neighbouring Bolivia and Paraguay have also struggled to contain fires that swept through woods and fields and, in many cases, got out of control in high winds after being set by residents clearing land for farming.
Demonstrations have taken place across Europe with action taking place in London, Paris, Barcelona, Amsterdam and Turin.
Protesters have also been seen out in Mumbai in India and Miami in the US.
Celebrities including Madonna, the footballer Cristiano Ronaldo and the Formula 1 champion Lewis Hamilton have tweeted their concerns about the fires raging in the Amazon.
The possibility of economic repercussions for Brazil and and its South American neighbours suggests the Amazon is becoming a battleground between Mr Bolsonaro and Western governments.