Marco Fossati says he opposes selling TIM Participacoes to comply with an antitrust ruling.
Move is likely the first step in taking measures against phone giant America Movil and broadcaster Televisa.
Second attempt to bring suit against rival MTN Group, whom it accuses of of "corrupt acts" to win licence.
More changes likely coming in widely expected management shake-up.
Threat to extend industrial action follows company terminating contracts of 59 employees for failing to return to work.
Latest executive at a state-owned firm to have his fate sealed as China tries to root out corruption.
Damages are latest turn in global patent litigation between the two mobile giants.
Spanish telecom group lags far behind former monopoly and arch-rival America Movil.
Claim unfair treatment following the sale of the company's mobile phones business to Microsoft Corp.
The sale set to boost Nokia's net cash position to nearly €8 billion from around €2 billion in the third quarter.
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