Brazilian state-owned energy company Petrobras has been given a green light from environmental regulator Ibama to drill an exploratory well near the mouth of the Amazon River, sparking fierce criticism from conservationists just weeks before Brazil hosts UN climate talks.

The licence, announced on October 20, permits drilling in block FZA-M-059, situated in deepwater off Amapá state, 500km from the Amazon River mouth and 175km from the coastline on the Brazilian Equatorial Margin.

According to Petrobras, operations are scheduled to commence immediately with an estimated duration of five months.

"We hope to obtain excellent results from this research and prove the existence of oil in the Brazilian portion of this new global energy frontier," CEO Magda Chambriard said in a statement.

The approval concludes a nearly five-year licensing battle that exposed rifts within President Luiz Inácio Lula da Silva's administration between energy ambitions and environmental commitments. The exploration block was auctioned by the government back in 2013.

Petrobras said it satisfied all requirements established by Ibama, fully complying with the environmental licensing process. In August, the oil firm conducted an on-site Pre-Operational Assessment, during which Ibama verified the company's capabilities and emergency response plan effectiveness.

However, environmental organisations swiftly condemned the approval, arguing it undermines Brazil's credibility just as it gears up to host world dignitaries for the COP30 climate negotiations in the Amazonian city of Belém on November 10-21.

"The approval sabotages the COP and goes against the role of climate leader claimed by President Luiz Inácio Lula da Silva on the international stage," Brazil's Climate Observatory said, as quoted by AFP.

"The decision is disastrous from an environmental, climate, and sociobiodiversity perspective.”

The Climate Observatory announced that civil society organisations will pursue legal action to challenge the decision, based on "illegalities and technical flaws" in the licensing process.

"It's sabotaging the climate agenda, as Petrobras is seeing this licence as the first of a series of other licences in Foz do Iguaçu and throughout the Equatorial Margin. And it's sabotaging Brazil's leadership at COP30," said Suely Araújo, public policy coordinator at the Climate Observatory and former Ibama president, as quoted by Folha de S. Paulo.

Greenpeace Brazil's Oceans coordinator, Mariana Andrade, quipped that, "on the eve of COP30, Brazil dresses in green on the international stage, but is covered in oil at home.".

The licensing process proved contentious within government ranks. In April 2023, Ibama's technical department recommended shelving the application, but agency president Rodrigo Agostinho reportedly brushed off that recommendation.

Documents from February showed an opinion signed by 29 Ibama technical staff maintained the recommendation to "deny the environmental licence", pointing to the risk of "massive biodiversity loss in a highly sensitive marine ecosystem", according to AFP.

In September, Ibama approved the pre-operational environmental assessment, despite Petrobras failing to demonstrate it can "reliably protect fauna in the event of an oil spill" and stated a new fauna simulation would occur "after the licence is issued."

Meanwhile, government officials aligned with Lula celebrated the authorisation. Mines and Energy Minister Alexandre Silveira said Brazil “cannot give up on exploring” its potential in crude oil production.

“We have made a firm and technical defence to ensure that exploration is carried out with full environmental responsibility, within the highest international standards, and with concrete benefits for Brazilians," said Silveira.

Senator Randolfe Rodrigues, the government leader in the upper chamber, hailed October 20 as a "historic day" for the country, saying the measure would enable "research for the discovery of riches such as oil, which can and will be decisive for our present and our future."

The Amapà region shares geological characteristics with neighbouring Guyana. There, ExxonMobil has developed substantial offshore fields since massive oil finds in 2015, transforming the small nation into a major oil producer within less than a decade.

Lula has long argued that oil revenues will help fund Brazil's climate transition and has defended exploration while continuing to position himself as a global climate leader.