* JPMorgan-led rescue plan proving difficult - sources
* Funds open to Passera plan but no commitment - sources
* No investment to be approved before Dec. 4 vote - source (Adds details, quotes)
By Pamela Barbaglia
LONDON, Oct 7 (Reuters) - A former Italian minister is preparing an alternative rescue plan for Monte dei Paschi di Siena amid signs that a 5 billion euro ($5.6 billion) recapitalisation arranged by JPMorgan is not getting investor support, three sources said.
Corrado Passera, who as well as being a former industry minister served as chief executive of Intesa Sanpaolo, is working with private equity firms including Warburg Pincus on a plan that includes a reserved capital increase of 2.0-2.5 billion euros, the sources said.
Two of the sources said none of the funds approached by Passera had committed to backing the plan and while they were open to doing a deal, this was subject to due diligence. Another source said no deal was imminent.
It is far from certain that Monte dei Paschi will turn to Passera, who was not immediately available for comment, or that his scheme would stand a better chance of success than JPMorgan's, one of the sources said.
And a source close to the JPMorgan-led consortium of investment banks said they were pressing ahead with their plan and were confident it would succeed.
The sources said private equity funds who have been working with Passera trust his ability to turn around the Siena-based bank, the world's oldest, which in July emerged as the weakest lender in the latest round of European stress tests.
Monte dei Paschi's board rejected in July a last-minute attempt by Passera to put forward a rescue plan backed by Swiss investment bank UBS, a long-standing adviser to the Tuscan bank. It approved instead the privately-backed rescue arranged by JPMorgan with the help of Mediobanca.
However, the deal has since ran into trouble, senior bankers say. A preliminary survey of investors over the summer found scant interest in a third cash call in as many years, while analysts have questioned the feasibility of a capital raising that totals 10 times the bank's current market value.
Last month, Monte dei Paschi abruptly replaced chief executive Fabrizio Viola with the head of Bank of America Merrill Lynch in Italy, Marco Morelli, in the hope of winning investors confidence and is now studying a debt-to-equity conversion to cut the size of the share sale.
JPMorgan is also looking for investors to back a reserved share sale but has yet to find any, several sources said.
Recent talks with a sovereign wealth fund fell through, one of the sources said, raising fears the bank may need state aid.
Most foreign investors are unwilling to commit any cash until a Dec. 4 referendum on constitutional reform that could unseat Prime Minister Matteo Renzi's government, bankers say.
"No investment committee will ever approve a deal for Monte dei Paschi without knowing the outcome of the Italian referendum," an investor close to the bank said. ($1 = 0.8951 euros) (Editing by Alexander Smith)