MILAN (Reuters) - Monte dei Paschi di Siena is preparing to close 50 branches in line with commitments taken with European Union authorities under its restructuring plan through 2021, according to a copy of a letter the state-owned bank sent to unions. The letter dated Sept. 15 seen by Reuters said the closures would lead to cutting 70 staff out of a total of 843 affected by the decision. The 70 people will be reallocated within the bank’s network, it said.Italy’s Treasury, which owns 64% of Monte dei Paschi following a bailout in 2017, is discussing a sale of the Tuscan bank to UniCredit.In announcing the exclusive negotiations at the end of July, UniCredit CEO Andrea Orcel had said a decision could be expected by mid-September, but sources close to the matter say reaching an accord is complex and will require longer. UniCredit has agreed to consider taking on only “selected parts” of Monte dei Paschi to boost its presence in the Tuscany, Veneto, Lombardy and Emilia Romagna regions.