(Recasts lead, adds source material, analyst)
PARIS/MILAN, Sept 13 (Reuters) - An Italian watchdog ruling that Vivendi has de facto control of Telecom Italia has strengthened Rome's hand as it considers using special powers that could trigger asset sales.
Billionaire Vincent Bollore's Vivendi, which owns 24 percent of Telecom Italia (TIM) and controls two-thirds of its board, denies it controls the former monopoly.
Vivendi's influence in Italy came under close political and regulatory scrutiny after it became No. 2 shareholder in Italy's biggest private broadcaster Mediaset with a 29 percent stake.
Italy's government is looking into whether Vivendi breached an obligation to notify it of its effective control of TIM, which is considered a strategic national asset.
If de facto control of TIM is shown, the government may conclude it can exercise so-called "golden powers", ranging from a fine to possibly demanding key assets be sold.
Market watchdog Consob ruled on Wednesday that the French group did exercise de facto control over TIM and a source close to the matter said on Thursday this played into Rome's hands.
"If there's no control there's no way the government can use golden powers against Vivendi," the source said.
Vivendi is about to notify Rome on its position in TIM but will reiterate it exercises only "management and coordination", a French source said.
Any acknowledgement of de facto control could force the French group to consolidate TIMs net debt pile of around 25 billion euros ($30 billion).
French markets watchdog AMF said on Thursday it had asked Vivendi to provide a detailed analysis to explain why it does not believe it controls Telecom Italia.
A forced sale of TIM's assets would be politically and commercially sensitive.
Politicians have been calling on and off since 2006 for TIM's prized backbone telecom network to be transferred to a state-controlled entity to create a neutral platform.
Meanwhile, TIM faces an assault on its core business from state-controlled utility Enel which is rolling out a fast internet network.
Service provider Sparkle is seen as a particularly sensitive asset because of its submarine network which connects to countries in Europe, the Mediterranean and the Americas.
A French source close to the matter said on Thursday that selling TIM's backbone network was not on the agenda, but added there were several options for Sparkle.
"It could be sold or it could become a separate entity within TIM under the leadership of an Italian leader," the source said.
Rome, currently caught up in a row with Paris over a deal to take control of France's STX shipyards, is expected to decide later this month on whether it should have been notified.
The French source said if a deal is reached between Italy and France over STX it would ease pressure on Vivendi over TIM and some analysts have said Vivendi is likely to name an Italian as TIM's CEO to appease Rome.
Separately, Italy's communications regulator AGCOM has called on Vivendi to cut its holding in either Mediaset or TIM to below 10 percent arguing having both breached Italian rules meant to prevent concentration of power.
Vivendi, which has appealed the ruling, has told AGCOM it will take a series of measures to meet the watchdog's concern, including transferring a stake of at least 19.19 percent of Mediaset shares to a trust. ($1 = 0.8415 euros) (Additional reporting by Mathieu Rosemain in Paris and Alberto Sisto in Rome; Editing by Toby Chopra and Alexander Smith)