RIO DE JANEIRO, June 17 (Reuters) - Exxon Mobil ( XOM )

and Chevron ( CVX ) on Tuesday took their first steps toward

eventually exploring oil in Brazil's Foz do Amazonas basin,

scooping up offshore blocks auctioned by the country in the

promising but environmentally-sensitive area.

The move marks the first recent endeavor from companies

other than Brazil's state-run oil giant Petrobras in

the ecologically biodiverse area, triggering backlash from

environmentalists who say it will increase the risk of

contamination of water sources and ecosystems that both wildlife

and Brazilians depend on.

Plans by Chevron ( CVX ) partnering with China's CNPC and Exxon with

oil giant Petrobras to drill for oil in Foz do Amazonas basin,

located off the coast of the Amazon rainforest, are

controversial due to the environmental importance of the region

and have faced delays in obtaining permits.

Two consortia involving Petrobras and Exxon Mobil ( XOM ) secured

ten blocks in total, with the Brazilian company acquiring five

blocks as operator, while the U.S. giant purchased the other

five as operator.

Chevron ( CVX ) in a consortium with China's state-owned CNPC

acquired a total of nine blocks, with Chevron ( CVX ) as

operator.

The area, home to vast coral reefs and coastal Indigenous

communities, is considered a frontier for oil exploration as it

shares geology with nearby Guyana, where Exxon Mobil ( XOM ) is

developing huge fields.

The auction result was celebrated by Brazil's Mines and

Energy Minister Alexandre Silveira, who said that exploration in

the Foz do Amazonas region was a "winning ticket" to reduce

poverty in northern Brazil.

"The interest from the U.S. companies, Chevron ( CVX ) and Exxon,

which already operate in Guyana, demonstrates that our potential

is gigantic," Silveira said in a statement.

LICENSING HURDLES

Petrobras has long been seeking clearance to drill in the

area. A decision by environmental agency Ibama last month let it

move a step closer to the goal, but came with an important

caveat for future permits in the area.

Chief Executive Magda Chambriard told Reuters earlier this

month she believes Petrobras will clear the last step to getting

a permit to drill in the second half of July.

"We scooped up what we wanted and seeing more companies

getting in, the majors, puts more pressure on the license for

exploration in the Equatorial Margin to be granted," a Petrobras

source said, referring to a broader offshore region of which Foz

do Amazonas is a key basin.

Silveira said he was certain Ibama would speed up the

process of granting licenses after the auction, which happened

as Indigenous organizations and non-governmental organizations

like the Arayara Institute protesting outside of the auction

venue against what they called "doomsday auction."

"Drilling new wells will increase the risk of environmental

disasters, worsen the climate crisis and deepen inequalities,"

Greenpeace Brasil's oceans coordinator, Mariana Andrade, said in

a statement.

Brazil's government is set to obtain 989 million reais

($180.79 million) in signing bonus for auctioning off 34 blocks.

($1 = 5.4704 reais)