MILAN (Reuters) - State-backed Poste Italiane is ready to increase its recently acquired stake in Telecom Italia (TIM), three sources said, in a move that would strengthen its position in any potential M&A deal involving the phone group.

The financial conglomerate led by former JPMorgan banker Matteo Del Fante said on Saturday it was replacing state lender CDP as a leading TIM shareholder by taking CDP's 9.8% stake.

After moving swiftly to secure the stake, Poste is assessing all potential options and has not yet taken any decision on future moves, the sources said.

Poste, which offers mobile phone services through its Poste Mobile unit but doesn't own its own network, declined to comment. It will present its strategy update on Friday.

The stake purchase comes ahead of expected consolidation in Italy's telecoms sector, where price competition has been eroding profit margins for years, making it hard for firms to sustain the necessary investments.

The slimmed-down TIM has already drawn M&A interest.

Representatives of rival French telecoms firm Iliad and private equity firm CVC approached Italian government officials about their respective plans for TIM not long before Poste's decision to step in, sources have previously said.

The government has special vetting powers on TIM and must authorise any purchase of a stake exceeding 3%.

Having putting on hold any consideration of approaches for TIM before Poste's arrival, Rome is not ruling out a tie-up between Iliad and TIM, Treasury Junior Minister Federico Freni said over the weekend, adding any deal should have an industrial rationale.

Any deal involving TIM would concern the entire company because the government opposes separating its consumer and corporate businesses, one of the first three sources, and a fourth person, said.

Poste's investment comes after TIM last year stabilized its finances by cutting debt through the sale of its prized landline grid to a consortium led by U.S. fund KKR, under a government-backed plan.

Poste is ready to ready to enter into discussions with all relevant stakeholders, one of the sources added.

TIM's main investor, French media group Vivendi, is open to selling its 24% stake after failing to halt TIM's landline grid sale. It is refusing to engage with TIM CEO Pietro Labriola.

By upping its holding Poste would be able to ensure a significant state-sector presence in TIM's capital even after any tie-ups.

In announcing its investment in TIM on Saturday, Poste said the operation was aimed at "creating synergies between the companies and favouring, with all the players involved, the consolidation of the telecommunications market in Italy".

(Reporting by Elvira Pollina, Valentina Za and Giuseppe Fonte, editing by Gavin Jones/Keith Weir)