Citigroup Inc.'s (C) Japanese private equity arm has restarted efforts to sell the country's largest call center company by market share, with the first round of bidding due to close Sep. 1, a person familiar with the deal told Dow Jones Newswires Friday.

The move to sell Bellsystem24,valued by Citi at about $1.5 billion, comes as the U.S. bank sheds a raft of operations in Japan that it considers to be non-core assets, part of efforts to bolster its capital base in the wake of the global credit crunch.

Nikko Principal Investments, Citi's Japan private equity arm, is hoping to offload the asset by November, the person said.

According to various media reports, private equity firms such as U.S.-based Kohlberg Kravis Roberts & Co, European fund Permira Advisors Ltd and Japanese trading firm Itochu Corp. (8001.TO) are interested in taking part in the bidding.

Earlier this year, Citi agreed to sell Nikko Asset Management to Sumitomo Trust & Banking Co. (8403.TO) and brokerage Nikko Cordial Securities to Sumitomo Mitsui Financial Group Inc. (8316.TO) in separate deals for Y112.4 billion and Y545 billion respectively.

Citi initially sought buyers for Bellsystem24 late last year, the Wall Street Journal reported at the time, but tight credit conditions slowed the deal.

Nikko Principal initially owned 71.73% of Bellsystem24, and went on to buy all outstanding shares from IT services firm CSK Corporation and its subsidiaries after Nikko itself was acquired by Citigroup in 2004. The purchase valued Bellsystem24 at around Y151 billion. Bellsystem24, which was delisted in 2005, posts annual earnings before interest, taxes, depreciation and amortization in the range of $150 million to $200 million, said another person familiar with the company.

Itochu, Permiraand Citigroup declined to comment on the deal.

--By Tor Ching Li, Dow Jones Newswires; 813-6895-7565; chingli.tor@dowjones.com