MILAN (Reuters) - Monte dei Paschi di Siena's acquisition of bigger rival Mediobanca would be challenging to implement if the Tuscan bank's bid succeeded, Fitch Ratings said on Friday.

While any assessment is premature, Fitch said MPS' ratings would likely be unaffected in the short term under the proposed terms of the transaction.

However, the credit rating agency flagged risks Mediobanca could lose clients or staff given that MPS is perceived "as a weaker and less specialised peer" in corporate investment banking and wealth management.

"MPS' plan to operate both brands with a high degree of independence could mitigate these risks, but this faces execution risks," it said.