Telefonica has tipped €800 million more into the pot in its play for Brazilian operator Vivo, taking the total offer for Portugal Telecom's indirect stake to €6.5 billion.
But Portugal Telecom's board has refused to endorse even the revised offer, stating it doesn't reflect the strategic value of the assets.
Portugal Telecom previously rejected an initial €5.7 billion bid for its stake in Brasilcel, a joint venture between it and Telefonica that owns around 60% of Vivo.
The revised offer comes in two forms: one which would have Portugal Telecom sell the entire stake immediately; and another that would allow the operator to choose a time within the next three years to conduct the sale, WSJ.com said.
Despite objecting to the offer, Portugal Telecom's directors have had a change of heart over allowing the deal to be discussed by shareholders and have called a shareholder meeting to allow its investors to vote on the offer.
However, the transaction could prove a tough sell for Telefonica.
Vivo was responsible around half of Portugal Telecom's 1Q revenue, and is growing at a time when most of the operator's units are stagnant.
But, with Telefonica grappling with the same issues, both firms see Brazil as a growth driver.
Portugal Telecom has in the past made its own bid to acquire sole ownership of the JV, which was founded in 2001.