RIO DE JANEIRO, May 26 (Reuters) - Brazil's Petrobras

wants to review Braskem's ( BAK ) shareholders

agreement for possible changes to allow it more say in the

petrochemical firm's decisions, three sources close to the

matter at the state-run oil firm told Reuters.

Petrobras has a 47% voting stake in the petrochemical

company but has appointed four of 11 board members and one

director out of seven, numbers it considers small, according to

the sources.

Last week, Braskem's ( BAK ) majority stakeholder Novonor received a

non-binding proposal from a fund owned by businessman Nelson

Tanure to acquire control of the largest petrochemical company

in Latin America.

Novonor has been trying to sell its stake in Braskem ( BAK ) for

years, but has repeatedly failed to reach a deal.

Petrobras' objective would be to obtain a new agreement akin

to the one it got in Eletrobras, where it increased the number

of seats it appoints to the board of the former state-run firm,

expanding its influence.

In the event of a sale, Petrobras has preference rights to

buy Novonor's stake, but the sources said Petrobras has no

interest in increasing its voting share.

Petrobras wants instead to have a more active voice in the

management and operations of the petrochemical company,

regardless of who is the controlling partner, said the sources.

On Monday, Petrobras CEO Magda Chambriard said Tanure's

proposal is a move in the right direction.

"Whatever solution that works out will have Petrobras'

support," said Chambriard.

Braskem ( BAK ) and Petrobras did not immediately respond to

requests for comment.