* Rig leaser shunned Petrobras proposal made this week
* Filing seen as way to improve Petrobras contract offer
* Sources see some shareholders abstaining from ballot
By Guillermo Parra-Bernal
SAO PAULO, Feb 26 (Reuters) - Most shareholders in Sete Brasil Participações SA plan to endorse a proposal for the ailing rig leaser to seek bankruptcy protection after efforts to secure a long-term contract with sole client Petróleo Brasileiro SA failed, four sources familiar with the situation said on Friday.
Partners holding a combined 95 percent stake in Sete Brasil through an investment vehicle will hold a conference call at 10 a.m. (1300 GMT) in which they will vote on the creditor protection plan, said the sources, who requested anonymity to discuss the issue freely.
Votes equivalent to about 85 percent of Sete Brasil's 12 partners in the FIP Sondas vehicle endorse filing for bankruptcy protection, said the first source. But some could still abstain from voting on the plan because of their dual role as lenders and equity holders, the second and third sources said.
The ballot would give management of Rio de Janeiro-based Sete Brasil power to decide when and where to file for court protection, the first source said.
This week, state-controlled Petrobras, as Sete Brasil's sole client is known, sent a proposal that failed to assure the rig leaser's survival, the sources said. Under terms of the proposal, Petrobras would rent 10 rigs for five years, instead of 19 for 15 years originally, as well as cut lease rates by one-third.
The fate of Sete Brasil, which Petrobras, pension funds and other partners created in 2008 to manage the world's biggest deepwater drilling fleet, with orders of $89 billion, hinges on Petrobras' willingness to sign a long-term rent contract. Management of Sete Brasil recommended shunning the proposal, the sources said.
Sete Brasil did not comment. Petrobras did not have an immediate comment.
A bankruptcy filing by Sete Brasil is seen as a way to press Petrobras into signing a more favorable contract for the rig leaser. Petrobras Chief Executive Officer Aldemir Bendine and officials at the company's exploration and production division are at loggerheads over the Sete Brasil contract, with the latter wanting a collapse of the rig leaser, the sources added.
In turn, a collapse of Sete Brasil would be devastating not only for the investors that backed the project, but for dozens of shipbuilders supplying the company. More than 800,000 local shipbuilding jobs could be lost, triggering 40 billion reais ($10.1 billion) in losses, industry estimates show.
Petrobras, which owns 5 percent of Sete Brasil, will not participate in the vote, the sources said.
The government-backed project began to sour in 2014 when Petrobras and Sete Brasil became engulfed in a huge corruption scandal in Brazil. Fallout from the so-called Operation Car Wash scandal deprived Sete Brasil of long-term financing, forcing Brazil's top lenders to roll over about 14 billion reais in loans for the past 1-1/2 years.
Sete Brasil owes about 18 billion reais to banks, a national workers' severance fund and suppliers.
Members of FIP Sondas include pension funds Previ, Funcef and Petros, lenders Grupo BTG Pactual SA and Banco Bradesco SA, and investment firms such as EIG Global Energy Partners and Luce Venture Capital.
Other Sete Brasil shareholders include Caixa's workers pension fund, Funcef, and Fundação Valia, the workers' pension fund of mining company Vale SA. None could be reached for comment outside working hours.
The tussle has forced BTG Pactual and creditors, which include Itaú Unibanco Holding SA and Bradesco, to write off part of the value of their investments and loans to Sete Brasil.
This month, Itaú, Bradesco, Banco Santander Brasil SA and state lenders Caixa Econômica Federal and Banco do Brasil SA agreed to renew almost 15 billion reais' worth of standstill loans until May in exchange for access to 4.3 billion reais in collateral at government-backed naval fund CDFMM, sources said last week.
$1 = 3.9546 Brazilian reais Editing by Peter Cooney