By Carolina Mandl and Tatiana Bautzer
SAO PAULO, July 1 (Reuters) - Brazil's state-controlled bank Caixa Economica Federal SA is challenging a decision by corruption-ensnared conglomerate Odebrecht SA to include one of its units' foreign bondholders in its bankruptcy protection filing, according to a document filed in the court case.
Among the 21 Odebrecht affiliates that filed for the bankruptcy proceeding two weeks ago was Odebrecht Finance, the issuer of $3 billion in bonds guaranteed by the group's construction unit OEC.
Caixa said in the document, filed late on Monday, that Odebrecht's move to include those bondholders in the bankruptcy case was designed to reduce the voting power of other creditors.
"This seems to be a strategy by Odebrecht to use the bondholders' vote to approve a restructuring plan that most probably will be detrimental to other creditors in the same class," the document said. "We can deduce that the strategy aims to dilute the voting power of legitimate creditors."
According to Caixa's calculations in the court filing, based on a creditor list provided by Odebrecht, bondholders account for 29.7% of the conglomerate's debt with financial entities, including insurance companies, bondholders and banks.
The request, filed by law firm Felsberg Advogados on Caixa's behalf, asked the judge to exclude Odebrecht Finance from the bankruptcy protection filing.
Caixa helped trigger the conglomerate's bankruptcy filing by trying to execute guarantees on one of the conglomerate's units that would trigger cross-default clauses.
The state-owned bank and funds it manages have 5 billion reais in debt with Odebrecht, most of it unsecured. All state-owned banks, including Banco do Brasil SA and development bank BNDES, hold 17 billion in debt in the bankruptcy case.
Odebrecht, which filed for one of Latin America's largest-ever bankruptcy cases, with a total of 98.5 billion reais ($25.6 billion) in debt, had already begun a restructuring with bondholders in New York.
Odebrecht has hired Moelis & Co to restructure the bonds and had proposed a 70% discount on their face value, which was rejected.
The bondholder committee had asked for the stake in petrochemical producer Braskem SA as collateral in the restructuring, but the stake is already pledged as collateral to local banks.
If creditors reject the restructuring plan proposed by Odebrecht, the company would go to liquidation, according to Brazilian bankruptcy law.
Odebrecht SA and petrochemical producer Braskem SA agreed in 2016 with Brazilian, Swiss and U.S. prosecutors to pay the world's largest leniency fine, of at least $3.5 billion, in a widespread bribery case in Latin America. ($1 = 3.8418 reais) (Reporting by Tatiana Bautzer and Carolina Mandl in Sao Paulo; Editing by Will Dunham)