Biden landed in the Brazilian city of Manaus, in the heart of the world's largest jungle, on the penultimate leg of a valedictory South American tour before handing the keys of the White House to Trump in January.

The 81-year-old is the first sitting US president to visit the Amazon.

Dressed casually in a blue shirt and pants, Biden chatted on the tarmac with local dignitaries, including Brazilian Nobel-winning climate scientist Carlos Nobre before boarding a helicopter to fly over the rainforest.

Biden, who was accompanied by Secretary of State Antony Blinken and his daughter Ashley and granddaughter Natalie, will also visit a museum and meet Indigenous and local leaders working to protect the Amazon.

Ahead of his visit, part of the Democrat's attempt to cement his legacy in his last weeks in office, the White House announced that the US had hit its target of increasing bilateral climate financing to $11 billion a year.

It said that the figure reached this year was six times what the US was providing at the start of Biden's term in 2021.

The money, which helps developing countries adapt to climate change, has made "the United States the largest bilateral provider of climate finance in the world," the White House said.

"The fight against climate change has been a defining cause of President Biden's leadership and presidency," it added.

Biden arrived in Brazil from Peru, where he attended his last summit with Asia-Pacific leaders.

He has cut a diminished figure on his tour. All eyes in Lima were on Chinese President Xi Jinping who was received with greater fanfare.

At a meeting with Biden, the Chinese leader was already looking to the new Trump era, saying he was ready to work with the "America First" leader and hoped for a "smooth transition" in relations.

Trump has pledged to reverse Biden's climate policies and could again pull the United States, the world's second-biggest polluter, out of the landmark 2015 Paris Agreement on combatting carbon emissions, as he did during his first term.

On Saturday, he nominated a fracking magnate and noted climate change skeptic, Chris Wright, as his energy secretary.

Trump's return to power looms large over a G20 meeting of the world's biggest economies starting Monday in Rio as well as over stalled UN climate talks in Azerbaijan.

- Amazon fires -

The Amazon, spanning nine countries, is crucial to the fight against climate change due to its ability to absorb planet-warming carbon dioxide from the atmosphere.

But it is also one of the areas most vulnerable to climate change and environmental degradation.

This year it experienced the worst wildfires in nearly two decades, fuelled by a severe drought blamed in part by climate experts on global warming.

A recent study showed that the Amazon rainforest had lost an area about the size of Germany and France combined to deforestation in four decades.

Brazil's President Luiz Inacio Lula da Silva has pledged to put a stop to illegal Amazon deforestation by 2030.

Experts have warned that a second Trump presidency could undo progress on the transition to green energy made under Biden, giving heavy polluters like China and India an excuse to scale back their own efforts.

During his campaign, Trump pledged to "drill, baby, drill" and increase fossil fuel extraction. He even brushed off climate change just days before the vote.

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Amazon.com