FRANKFURT/LONDON (Reuters) - European insurers Allianz (>> Allianz) and Baloise Holding (>> Bâloise-Holding) and London-based buyout fund Cinven are finalising rival offers for Generali's (>> Assicurazioni Generali) Belgian unit ahead of a Sept. 8 deadline, sources told Reuters.

The deal could value the business at up to 500 million euros ($595 million) in what would be the Italian insurer's biggest divestment in its latest reorganisation.

Generali, Europe's third-biggest insurer, wants to wrap up the auction by mid-September finding a new owner for a business that provides anything from life insurance to car cover to a network of about 530,000 retail and corporate clients.

It is looking to sell the entire business to a single investor rather than break it up and carve out so-called "back books", which consist of existing contracts with no access to new clients, the sources said.

The Italian company said in November that it wanted to raise at least 1 billion euros by leaving 13 to 15 countries.

CEO Philippe Donnet said on Friday that he is "very confident" the group would meet that goal.

"The sale process is going well, there is a lot of interest for our assets," he told reporters on the sidelines of the Ambrosetti business conference in Italy.

Bermuda-based insurer Athene Holding (>> Athene Holding Ltd) is also vying for Generali's Belgian business, the sources said, adding that it might only be targeting the "back books".

Allianz, Baloise and Cinven are instead looking to buy the business as a whole, they said.

Generali, Allianz, Baloise, Athene and Cinven declined to comment.

The auction, which is being led by Deutsche Bank (>> Deutsche Bank), was launched this year as part of Generali's efforts to cut costs in weaker markets and boost profit.

Bidders were asked to submit non-binding offers in July, the sources said, with one adding that first-round bids valued the business at less than 500 million euros.

Generali has been present in Belgium for more than a century, having started operations there in 1901.

Its Belgian unit has 6.3 billion euros of assets under management and reported net profit of about 89 million euros in 2016, with total premium income rising 19.2 percent to 800 million euros.

Generali recently sold its Colombian business to Talanx Group and is working with BNP Paribas to find a new owner for its Dutch business.

It also planning to exit Portugal, the sources said, adding that the process will begin later this year.

Germany's Allianz recently formed a joint venture and strategic partnership with British insurer LV [LV.UL] to form the third-largest property and casualty insurer in Britain. It also took control of Nigeria's Ensure Insurance in a push for growth in Africa.

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(Additional reporting by Stephen Jewkes, Oliver Hirt and Valentina Za; Editing by David Evans and David Goodman)

By Arno Schuetze and Pamela Barbaglia