The wireless operator is listed on the Brazilian stock market, and 40 percent of its stock is publicly traded. Another threat that Telefónica had previously made, should it fail to secure ownership of Vivo, would be to launch instead a hostile bid for Portugal Telecom — even though such a move would face even stiffer resistance from the Portuguese government. The Spanish operator wants full control of Vivo to help increase its leadership in the Brazilian wireless market, where the number of cellphone subscribers rose 15 percent last year, as well as derive cost savings by merging Vivo with its fixed-line Brazilian business, Telesp.