The company has already made an offer of €6.7 billion, and Telecom Italia is also set to present a rival offer for the business.
Vivendi has scheduled a board meeting for tomorrow, and the revised offer could be presented before then.
European operators Telefónica and Telecom Italia are seeking ways to bolster their operations as they experience slowing growth in their domestic markets.
Telecom Italia already owns a mobile unit in Brazil, but the company is likely to exit the market if Telefónica secures GVT, as it will then struggle to compete with the larger providers.
No final decisions have been made, and Telefónica could still maintain its existing bid. Telecom Italia is reportedly planning to bid as much as €7 billion.
