By Silvia Aloisi and Andrea Mandala
MILAN (Reuters) - A 5 billion euro ($5.33 billion) rescue plan for Italian bank Monte dei Paschi di Siena <BMPS.MI> hung by a thread on Monday after Prime Minister Matteo Renzi's defeat in a referendum and pledge to resign.
The world's oldest bank, saddled with 46 billion euros of bad loans, needs to raise the money by the end of the month to avoid being wound down, but investors are reluctant to back the cash call after Renzi said he would quit following voters' rejection of his plans for constitutional change.
Monte dei Paschi, rated the weakest lender in European stress tests this summer, had planned to secure a firm commitment from one or more anchor investors and launch a share sale as early as Wednesday or Thursday.
However, investment banks deciding whether to underwrite the capital raise will wait for three or four days before making up their minds in the hope of a clearer political situation, two sources close to the matter said. Under a pre-underwriting deal, they can drop the transaction due to adverse market conditions.
Qatar Investment Authority (QIA), which could inject up to 1 billion euros in the Tuscan lender, and other big investors also want to have more visibility on what kind of government will succeed Renzi's and whether early elections are a possibility.
"The Qataris won't commit until there's clarity on the government," said a banker close to the consortium. "At the moment Monte dei Paschi is not in a position to speak to investors, they have nothing new to tell them … they need to wait until the Qataris make up their mind."
QIA declined to comment. Monte dei Paschi, which is due to hold a board meeting on Tuesday, had no immediate comment.
If Monte dei Paschi's private recapitalization plan fails, the Italian government is expected to step in and pump public money into the bank to avoid a crisis, bankers and European officials said.
The lender's shares fell 6 percent in late afternoon trade, dragging down the whole banking sector on concerns that instability in the euro zone's third-largest economy could ignite a wider financial crisis.
Renzi is expected to formally tender his resignation on Monday evening. The head of state will consult with party leaders before naming a new prime minister, with Economy Minister Pier Carlo Padoan seen as a possible candidate to replace Renzi. Snap polls next year cannot be ruled out.
Whether a few days will be enough to persuade investors to back Monte dei Paschi's third recapitalization in as many years remains unclear.
European officials and allies played down the prospect of a broader euro zone crisis. European Central Bank Governing Council member Ewald Nowotny said Italy, which unlike Germany and other European countries has used very little public money to prop up its lenders, might have to bail out some banks.
But he said market concerns about Italian lenders should be kept in perspective and any problems there were manageable.
Any state intervention to help Monte dei Paschi would entail losses for the bank's subordinated bondholders in line with European bank crisis rules - something Renzi's government had desperately sought to avoid to stave off the risk of a run on deposits and a domino effect engulfing other lenders.
It was not immediately clear to what extent retail investors, who hold 2.1 billion euros of Monte dei Paschi junior debt, could be spared in the event of a state rescue.
Even at the height of the euro zone's debt crisis, Italy had resisted calls to inject cash into its banks or ask for an EU bailout. But it is running out of private solutions to cure the sector, which is burdened by 360 billion euros of bad loans accumulated during a harsh recession.
Italy's 4.25 billion euro Atlas fund, created this year to help channel private funds into struggling banks, has seen its coffers dry up as banking crises mushroom around it.
Two banks from the Veneto region that were rescued with a 2.5 billion euro capital injection by the fund in the spring need another 2.5 billion euros in fresh capital soon. And four small lenders bailed out by healthier banks last year also need more money to clean up their balance sheets.
Meanwhile, a failure of Monte dei Paschi's cash call could complicate UniCredit's own capital-raising plans. Italy's largest bank by assets is expected to unveil on Dec. 13 a cash call for up to 13 billion euros, to be launched early next year.
(Additional reporting by Paola Arosio and Valentina Za in Milan, Maiya Keidan and Pamela Barbaglia in London, Tom Finn in Doha; Editing by Mark Bendeich, Anna Willard, Janet McBride, Philippa Fletcher)