According to FUP, more than 95% of its workers voted against the deal, disagreeing with the wage rise offered by Petrobras.
The union claims the proposed salary increase is inadequate and objects to the company's new strategy to divest $34.6 billion worth of assets by 2018.
The strike has been nicknamed Operation "Para Pedro" - "Stop Pedro" - in reference to chief executive Pedro Parente.
FUP
