(Adds PT statement on dos Santos's offer)
By Axel Bugge and Leila Abboud
LISBON/PARIS, Nov 12 (Reuters) - Private equity firms Bain Capital and Apax Partners have launched a bid worth 7.075 billion euros ($8.8 billion) to buy the Portuguese operating business of Portugal Telecom from Brazil's Oi, rivalling an offer from European telecoms group Altice .
Altice, the holding company of Franco-Israeli telecoms entrepreneur Patrick Drahi, made a bid last week which it said put an enterprise value on the PT Portugal business of 7.025 billion euros.
But Oi said in a statement it has now received a similar offer from Apax and Bain for the PT Portugal assets worth 7.075 billion euros, which Oi's board would now consider.
Oi is considering selling Portugal Telecom assets to reduce its debt of over $18 billion, which would effectively unwind a protracted merger of the two companies.
That deal soured after the Rioforte holding company of the Espirito Santo banking family, ultimately a shareholder in PT, defaulted on nearly 900 million euros ($1.14 billion) of debt owed to PT. Oi said it had not been aware of the debt before the deal and the fallout resulted in a renegotiation of the merger.
Oi is expected to use the proceeds of any PT Portugal asset sale to strengthen its hand in the further consolidation of the Brazilian telecoms market.
But Isabel dos Santos, the daughter of Angola's president, has sought to block Oi's sale of PT assets with an offer on Sunday for the Lisbon-listed holding company Portugal Telecom SGPS (PT SGPS) at 1.35 euros per share.
Under their merger the Portugal Telecom SGPS holding company owns a 25.6 percent stake in Oi and if dos Santos succeeds with the bid she would become a major shareholder. Portugal Telecom's operations in Portugal have already been transferred to Oi and are no longer in the holding company.
Dos Santos, which shares with Sonae control of Portugal's second-largest telecoms operator, NOS, has said she wants to keep the Oi-PT group intact.
Oi in turn has said it opposes dos Santos's bid for PT SGPS because it seeks to interfere with the merger between Oi and Portugal Telecom.
PT SGPS said in a statement its board would consider the dos Santos offer "if and when the draft prospectus and the draft launch announcement are submitted to it."
Against this complex background, Altice and the private equity firms are seeking to buy the operations of the once state-owned monopoly telecoms firm in Portugal. Both bids include earn-out payments worth up to 800 million euros related to future profit and cash generation targets.
PT Portugal still has a leading position in fixed telephony and broadband in the country, with a 52 percent share. It also holds 41.5 percent of the mobile market in terms of revenue, according to Citigroup, competing with Vodafone with 41.6 percent and Nos with 16.9 percent.
Altice already owns two small telecoms companies in Portugal, Cabovisao and Oni. (1 US dollar = 0.8037 euros) (Editing by Greg Mahlich)