U.S. private equity firm Bain Capital is finalizing a roughly 100 billion yen ($1.1 billion) deal to buy Japanese telemarketer Bellsystem24 from Citigroup Inc , three sources familiar with the matter said.

It would be the largest buyout by a foreign private equity firm in Japan in nearly two years.

Bain has beaten off rivals Permira

and a team of CVC Capital and Blackstone , which had also made offers in the final round of bidding for Bellsystem24, the sources said, speaking on condition of anonymity because the talks are not public.

Bain is working on final details and an official announcement could be made within the next few days, the sources told Reuters.

A deal is imminent, one of the sources said.

Bain had been tipped as the likely buyer when it secured exclusive negotiating rights earlier this month.

But the door was thought to be still open to the other bidders after the deadline for Bain's exclusive rights passed on November 6 with no deal announced.

Talks had been ongoing with the CVC and Blackstone team after the exclusivity period ended, and that team had improved its bid, one source familiar with the move told Reuters.

Citigroup put Bellsystem24 up for sale as part of a global effort to raise cash and replenish its capital. It has already raised more than $7 billion by selling other assets in Japan including a broker, a trust bank and a fund management arm.

The sale of Bellsystem24 initially drew strong interest from a number of private equity firms including Kohlberg Kravis Roberts & Co , which teamed up with trading house Itochu Corp <8001.T> before dropping out of the race.

The deal will likely reach or exceed 100 billion yen, sources said, making it Japan's largest buyout by a foreign private equity firm since March 2008, when Permira bought agrichemical company Arysta LifeScience Corp for more than $2 billion.

Bellsystem24 is Japan's largest telemarketing firm. It competes against Moshi Moshi Hotline Inc <4708.T> and Transcosmos Inc <9715.T> in Japan.

Bellsystem24 is now owned by Citigroup Capital Partners, which was known as Nikko Principal Investments, a private equity arm of brokerage group Nikko Cordial, which was bought by Citigroup in 2007.

Nikko Principal paid 220 billion yen to buy Bellsystem24 in 2004. The sale price would be lower than the purchase price but Citigroup had made returns from the investment by restructuring the company's debt to take some cash out, a method known as recapitalization.

Bain's financing will be supported by banking units of Mitsubishi UFJ Financial Group Inc <8306.T>, Mizuho Financial Group Inc <8411.T> and Sumitomo Mitsui Financial Group Inc <8316.T>, according to sources familiar with matter.

Bain's debt will be repaid through cash flow from Bellsystem24, which has raised concerns among Bellsystem24 employees about possible cost cuts and loss of jobs, an unnamed official at Bellsystem24 told Reuters.

A person with direct knowledge of the buyout said Bain's business plan would be based on Bellsystem24's growth and ruled out any job cuts.

Bain Capital last year outbid Japanese private equity firm Advantage Partners to buy D&M Holdings, the maker of Denon audio equipment, for $662 million.

Bain Capital opened an office in Japan in 2006.

($1=90.18 Yen)

(Additional reporting by Wakako Sato in Tokyo; Editing by Michael Watson)