French President Emmanuel Macron, the summit host, and Chilean President Sebastian Pinera, a visitor at the summit, said that the rainforest now being ravaged by the fires represents the "lungs" of the planet for its role in absorbing carbon dioxide and producing oxygen.
Macron said France within hours would provide military support in the region to fight the fires.
Macron and Pinera said the G-7 countries - the United States, Britain, Germany, Italy, Japan, Canada and France - were studying the possibility of similar aid to support Africa to fight wildfires in its rainforests.
Macron had threatened to block a new European Union trade deal with Latin America unless Brazilian President Jair Bolsonaro, a climate change skeptic, took serious steps to fight the Amazon fires. Under pressure from the international community to protect the environment, Bolsonaro on Sunday dispatched two C-130 Hercules aircraft to help douse the blazes.
Macron said the United States supported the aid to South American countries even though President Donald Trump skipped Monday's G-7 working session on the environment.
More than 75,000 fires covering the Amazon region have been detected this year, with a large number of them this month. Experts have blamed farmers and ranchers for the fires, accusing them of setting the fires to clear lands for farming.