Sources have said Italy's third biggest bank, which needs to raise 5 billion euros by year end to avert the risk of being wound down, is aiming to net between 1 billion euros and 1.5 billion euros from the conversion of subordinated bonds into shares.

Final results of the swap offer will be released by Monday, the bank said in a statement.

The Tuscan lender, which fared the worst in a European stress test of the sector this summer, is looking to raise the rest of the cash through a private placement to one or more anchor investors and a share sale on the market.

But a referendum this Sunday that could unseat the government of Prime Minister Matteo Renzi and sour market sentiment towards Italian banks has cast a pall over the privately-backed rescue scheme.

The bank has so far failed to secure a firm commitment from investors ahead of the referendum, with all opinion polls predicting a defeat for Renzi before a blackout on the publication of surveys was imposed on Nov. 18.

Chief Financial Officer Francesco Mele said this week the bank was hoping to win the backing of an anchor investor by Monday and sources have said Qatar Investment Authority could inject up to 1 billion euros in the bank, but wanted to wait for the outcome of the vote.

A source close to the matter said on Friday a consortium of investment banks that has signed a preliminary commitment to underwrite the cash call - which is expected to start on Dec. 7 or 8 - will meet the bank's management on Monday to decide whether to go ahead with the capital raise as planned.

A "no" vote could pave the way for state intervention to prop up the bank. Italy is discussing with the European Commission the terms of a state bailout that has already been requested and could be launched next week if needed, Italian daily Corriere della Sera reported on Friday.

That would almost certainly entail losses for the bank's subordinated bondholders, in line with tougher European rules for dealing with bank crises that came into force this year.

Corriere della Sera said Rome and the Commission were still debating to what extent retail investors who hold the bank's junior debt could be spared.

The EU Commission and the Italian treasury declined to comment.

(Editing by Elaine Hardcastle)

By Silvia Aloisi