LetterOne, the private equity firm backed by Russian billionaire Mikhail Fridman and his Russian partners, could invest $4 billion into debt-laden Oi, if it merges with rival TIM Participacoes.

Fixed-line giant Oi, which also has a smaller mobile business, said its adviser BTG Pactual received a letter on Friday (23 October) containing a proposal from LetterOne.

The private-equity fund wants exclusive negotiations with Oi, as it eyes a potential combination with Telecom Italia’s local unit, TIM Participacoes. If the consolidation process proved successful then LetterOne would invest a hefty $4 billion in Oi.

The private equity firm holds a 48 per cent stake in VimpelCom and 14 per cent share in Turkecell, indicating it is a heavyweight player. In addition, the firm has separate plans to invest $16 billion in the US and Europe telecoms and technology business.

Oi said it will carefully evaluate LetterOne’s proposal. Oi and TIM Participacoes are two of Brazil’s four leading operators. The other two are America Movil-backed Claro and Telefonica’s Vivo.

Consolidation of the country’s mobile market has been mooted for some time. Indeed Oi has been linked last year to a joint bid for Telecom Italia’s Brazilian arm TIM, in partnership with America Movil and Telefonica.