Citigroup Inc., the recipient of three U.S. government bailouts, is seeking bidders for its Japanese asset management unit, four sources said.

Citigroup started the auction process to sell Nikko Asset Management Co. this week and invited bids from Japanese banks, including Mizuho Financial Group Inc., the sources said, declining to be identified because they aren't authorized to publicly discuss the deal.

Citigroup in January put Japanese units including Nikko Asset on a list of businesses flagged for eventual sale, about a year after buying them as part of the ¥1.6 trillion acquisition of Nikko Cordial Corp. The U.S. government has channeled $45 billion into Citigroup and agreed to take a 36 percent stake after five quarterly losses.

Mizuho, Japan's second-largest bank by revenue, is considering bidding for Nikko Asset, the sources said. Nikko Asset, run by Chief Executive Officer Timothy McCarthy, managed ¥9.1 trillion as of Dec. 31.

Atsuko Yoshitsugu, a Tokyo-based spokeswoman for Citigroup, and Mizuho spokeswoman Masako Shiono declined comment.

Citigroup may seek partners for Nikko Asset and Nikko Cordial Securities Inc., or sell them in an initial public offering, other sources said earlier, citing an internal memo sent by Douglas Peterson, the company's chief executive for Japan, to employees on Feb. 25.

The U.S. company is also considering seeking buyers for Nikko Cordial, the sources said.