By Valentina Za and Gianluca Semeraro

TRIESTE, Italy (Reuters) -UniCredit on Thursday threw its weight behind rebel Generali investor Francesco Gaetano Caltagirone, three sources said, in a move that may soften government opposition to a takeover bid for Banco BPM.

Although Caltagirone was effectively defeated in Thursday's shareholder vote to pick a new Generali board, CEO Andrea Orcel positioned UniCredit with a front which has government support and is conducting multiple battles in Italian finance.

The Generali vote handed a victory to top shareholder Mediobanca, which secured 10 board seats and another term for CEO Philippe Donnet. Caltagirone only won three seats.

Caltagirone's main ally is investment company Delfin, an investor in UniCredit. Together they own 17% of Generali and 27% of Mediobanca.

Delfin and Caltagirone recently acquired also nearly 20% of state-backed lender Monte dei Paschi di Siena (MPS), which has announced a takeover offer for Mediobanca.

The bid followed UniCredit's swoop on BPM in November. That derailed government plans to combine BPM with MPS.

The conservative government of Prime Minister Giorgia Meloni last week threw a spanner in the wheels of UniCredit's bid for BPM with a set of conditions which UniCredit says could be harmful.

The BPM bid starts on Monday. UniCredit, which has a right to pull it until June 30, has engaged with the government over the conditions.

UniCredit faces another hurdle for Credit Agricole, BPM's main investor, which has secured Rome's blessing to increase its stake close to 20%.

Orcel fell out with Italy's previous government when he walked away from a deal to buy MPS in late 2021. He has failed to rebuild relations with Meloni's executive.

With its BPM bid struggling, Orcel built a stake in Generali in recent months which has reached 6.7%.

The stake was widely seen as a way to boost Orcel's bargaining power in Italy's fast-moving M&A game, and UniCredit had been expected to abstain in Thursday's vote.

Instead after a board meeting on Wednesday where the government's conditions for BPM were discussed, Orcel sided with Caltagirone, according to three people close to the matter.

UniCredit declined to comment. One of the people said the bank saw as potentially beneficial changes at Generali, Italy's biggest insurer and one of its most prestigious financial asset.

(Reporting by Valentina Za and Gianluca Semeraro; Editing by Bernadette Baum and David Evans)