Chief Executive Pietro Labriola is seeking a turnaround of the debt-laden former phone monopoly through the sale of the group's domestic landline grid, the company's most prized asset, to slash its 26 billion debt pile amid rising interest rates.

But his efforts have been thwarted so far by valuation issues, with top investor Vivendi calling into question the sustainability of the remaining business.

Speaking to analysts, Labriola said the service part of the company's business, which includes its domestic consumer and enterprise service operations and TIM's Brazilian unit "is already sustainable" as a separate entity.

Labriola said the service arm would generate "combined pro-forma core profit after lease significantly above 3 billion euros in 2023".

(Reporting by Elvira Pollina; Editing by Keith Weir)