MILAN, Aug 21 (Reuters) - Italy's Monte dei Paschi di Siena may raise a much-needed 2.5 billion euros ($2.5 billion) in steps, Italian daily La Repubblica reported on Sunday, as the bank looks to boost its capital by mid-November.

The collapse of Prime Minister Mario Draghi's national unity government in July, which has propelled Italy towards an election on Sept. 25, has made the capital-raising plan more complicated for the world's oldest bank.

According to La Repubblica, the bank may get 1.6 billion euros already committed by Italy's treasury by Nov. 12.

Later on, it could get additional "injections of private funds, perhaps from the longed-for buyer that the Treasury has been seeking for years", the paper said. Monte dei Paschi was not available for comment.

In mid-July, Monte dei Paschi's CEO publicly said the bank would raise the 2.5 billion euros via a capital increase to be executed under an "all or nothing" condition.

But in documents published on the bank's website in mid-August ahead of a Sept. 15 shareholders meeting due to approve the rights issue, MPS dropped the "all or nothing" condition for the cash call.

Repubblica said this change could be linked to MPS' intention to complete the cash call in steps, or could be aimed at reducing the risks for the banks in the underwriting consortium for the capital increase.

In the same documents, the bank said it was confident of completing the planned cash call between the end of October and the beginning of November, "if market conditions allow it".

The bank said it could add more investment banks to the group of eight lenders already lined up for the cash call, and added it may sign agreements with anchor investors and "other investors" to underwrite part of the rights issue.

A source with knowledge of the matter told Reuters in late July that the Treasury was determined to complete the bank's capital raising despite the political chaos.

($1 = 0.9966 euros) (Reporting by Francesca Landini; Editing by David Evans and Jan Harvey)