LONDON/MILAN (Reuters) - Newly-formed Banco BPM (>> Banco BPM SpA) is considering a sale of its asset manager Aletti Gestielle SGR as it seeks to "optimise" the Italian bank's assets, sources told Reuters on Thursday.

Italy's third largest bank, formed last year by the merger of cooperative lenders Banco Popolare and Banca Popolare di Milano, has asked Barclays to kick off a "general review of the business", a spokeswoman for the bank said, adding that this was not focused on any specific unit.

The sources said Aletti Gestielle is likely to pursue a combination with Anima Holding, another Italian asset manager in which BPM is the leading investor with a 14.67 percent stake, although other bids would be sought.

Formal negotiations have yet to kick off, they added.

Anima Holding and Barclays declined to comment.

Aletti Gestielle, formerly part of Banco Popolare, has around 17 billion euros (14 billion pounds) of assets under management and could fetch about 500 million euros, the sources said.

The business, which has more than doubled its assets under management over the past five years, may be sold before the summer, one of the sources said.

Anima, which one of the sources described as a "natural buyer" for Aletti Gestielle, ranks as Italy's largest independent asset manager with almost 73 billion euros of assets under management and a market value of 1.7 billion euros.

Anima's Chief Executive Marco Carreri told Reuters in July that his firm was looking at Aletti Gestielle as well as Arca as possible M&A targets.

Anima, which has Poste Italiane as another big investor with a 10.32 percent stake, shares the same domestic focus and a similar business model to Aletti Gestielle, the sources said.

However, Banco BPM is expected to sound out other bigger industry players such as Amundi (>> Amundi S.A.) and Aberdeen Asset Management (>> Aberdeen Asset Management plc).

Amundi, which has a market value of 8.7 billion euros, recently outbid a consortium of Anima, Poste Italiane and Italy's state lender Cassa Depositi e Prestiti in the takeover battle for UniCredit's (>> UniCredit SpA) Pioneer.

Mid-sized asset managers in Europe are joining forces as they scramble to gain global scale, streamline operations and cope with declining fees and tougher regulatory scrutiny.

In Britain asset manager Henderson Group (>> Henderson Group Plc) agreed to buy U.S. rival Janus Capital Group (>> Janus Capital Group Inc) in October in a $6 billion deal to cut costs and boost profits amid growing competition from index funds.

(Editing by Alexander Smith)

By Pamela Barbaglia, Maria Pia Quaglia and Andrea Mandala