The two leaders have persistently downplayed the pandemic even as their countries suffered from the world's most deadly outbreaks
Victory by Democrat Joe Biden in next week's US presidential election could put the environment and human rights at the top of the country's agenda with Brazil, complicating relations with Brazilian President Jair Bolsonaro and jeopardizing trade, diplomats and analysts say.
If Biden wins Tuesday's vote, Bolsonaro would lose a diplomatic ally and find himself isolated in his approach to the Covid-19 pandemic, which he modeled on US President Donald Trump's disregard for the gravity of the virus.
The two leaders have persistently downplayed the pandemic even as their countries suffered from the world's most deadly outbreaks.
Pressure from Biden to curb deforestation in the Amazon and concern for climate change would be a major departure from Trump's approach and could cause frictions with Bolsonaro, according to Mike Shifter, president of the Inter-American Dialogue, a Washington think tank that focuses on relations within the Americas.
"There are people in the Democratic Party that would like to go after Bolsonaro and be very tough with him on this issue, and join forces with the Europeans to apply significant pressure," Shifter said in a telephone interview.
Concerns for LGBT rights, and those of women and indigenous people, which were not on the agenda under Trump, will be raised by a Biden administration, Shifter said.
Brazil's marginalized communities, including LGBT people and Afro-Brazilians, say violence against its members has increased under a president known for homophobic and racist comments during his time as a congressman.
Indigenous leaders say that Bolsonaro's plan to economically exploit the Amazon has encouraged invasions of reservation lands by illegal loggers and gold miners.
During last month's first presidential debate against Trump, Biden said the rainforest was being "torn down" and proposed countries offer Brazil $20 billion to stop deforestation or face "economic consequences."
Bolsonaro slammed the statements as "coward threats" of sanctions. The president's office did not immediately respond to a request for comment.
Rubens Barbosa, a former Brazilian ambassador to Washington, expects Brazil's exports to suffer if Biden joins efforts by European nations to combat Amazon deforestation. US backing could strengthen calls in Europe for the boycotts of food exports from Brazil, he said.
Brazil's agricultural produce accounts for one quarter of its exports. Despite close ties between Bolsonaro and Trump, Brazilian exports to the United States, its second largest trade partner after China, fell by 31.5% in the first nine months of this year to their lowest level in a decade partly due Washington's protectionist policies.
Although the United States is more of a competitor than a major export market for Brazil's key agricultural commodities, a critical stance from a newly elected president would pile further pressure on major buyers of Brazil's beef and soy, which have been linked to deforestation.
That could leave Brazil ever more reliant on China, frustrating Bolsonaro's conservative base, analysts said.
"This could have concrete consequences for Brazilian agricultural exports and the financing of projects in Brazil," Barbosa said.
The US and Brazilian governments signed trade and investment agreements last week.
Biden is unlikely to undo those advances, but plans for a free trade deal heralded by Bolsonaro won't happen if the Democrat becomes president and puts the environment at the forefront of his agenda, said Eric Farnsworth, vice president of the Americas Society and Council of the Americas, dedicated to promoting business in the hemisphere.
Biden will try to maintain good relations with Brazil for the sake of US interests in South America, Shifter added.
When it comes to opposing China's growing influence in Latin America, there will be little change, because it is one issue in Washington today where there is bipartisan support, Farnsworth said.
But Biden likely will take a softer approach and drop Trump's aggressive stance of forcing Brazil and other nations in the region to choose between the United States and China.
The Trump administration has stepped up efforts to convince countries to exclude Chinese telecom equipment giant Huawei Technologies Co from the 5G market, citing security concerns, and it has offered credit for carriers to buy from companies outside China.
With Biden in the White House, countries like Brazil that do business with Huawei will not be cut off, Farnsworth said.