The three have not expressed a formal interest in buying the stakes, the source, who is familiar with the thinking of Telecom Italia shareholders, added.

The board of Telecom Italia is meeting on September 19 and its chairman Franco Bernabe is seeking a new investor ahead of the meeting.

AT&T declined to comment. Sawiris, America Movil and Telecom Italia were not immediately available for comment.

Shareholders have so far shot down two merger plans that Bernabe brought to the board. The first was a proposal by Sawiris last year to take a stake in Telecom Italia through a 3-billion-euro capital hike, while the second involved a merger with Hutchison Whampoa's Italian mobile unit.

But a sector shake-up triggered by the $130 billion deal between Verizon and Vodafone is putting Telecom Italia, vulnerable due to its low profitability and high debt, back into the frame.

Telecom Italia is 22.4 percent-owned by Telco, which is in turn controlled by Italian banks Mediobanca and Intesa Sanpaolo, domestic insurer Generali and Spain's telecoms operator Telefonica.

Mediobanca has openly said it is preparing for a sale after writing down its indirect investment in Italy's biggest telecoms group to around current market price.

Shareholders have until September 28 to exercise the option to leave the Telco pact early.

Shares in Telecom Italia opened up on the back of continued speculation about the future of the Italian fixed-line giant and extended gains to rise 6 percent at 0.59 euros by 1005 GMT.

"The acceleration in the sector's consolidation and Telecom Italia's and its holding company's difficulties support the idea of extraordinary operations," ICBPI brokerage said in a note.

"The likely exit of Mediobanca and Generali from the Telco pact by a September 28 deadline boost speculation on the stock."

Italian daily la Repubblica said on Thursday Bernabe planned to propose to the board a reserved capital increase to bring in a new investor.

(Additional reporting by Valentina Za and Danilo Masoni,; Writing by Lisa Jucca; Editing by Anna Willard)

By Paola Arosio