TIM has been caught in a battle since early last year between top shareholders Vivendi and activist fund Elliott over how to revive Italy's biggest phone group, an underperforming business saddled with 25 billion euros ($28.34 billion) of debt.

The former state phone monopoly said it would revamp its domestic business, grow its Brazilian unit and pursue several initiatives to unlock value.

Those include a mobile sharing agreement with Vodafone in Italy announced earlier on Thursday, and negotiations with smaller broadband rival Open Fiber on "all possible options including a full business combination on fixed network".

TIM said group organic earnings before interest, taxes, depreciation and amortisation (EBITDA) and service revenues would decrease by a low single digit this year, but grow at a low single digit rate in 2020 and 2021.

For 2018, the company reported a 3.6 percent drop in group revenues to 19.1 billion euros, roughly in line with an analyst consensus provided by the company. Organic EBITDA, excluding non-recurring items, fell 3.4 percent to 8.1 billion euros, in line with expectations.