The BPO business is run by Mumbai-based Citigroup Global Services (formerly e-Serve) and is reported to be valued at over $1 billion.

Several big players - including IBM, Automatic Data Processing, Infosys, EDS, Capgemini and private equity firms such as Blackstone and General Atlantic - are now thought to be out of the running.

Genpact is reported to be leading the race to take over the unit.

Local press reports suggest Citigroup may sell 80% of the business and keep hold of the rest until the company is listed.

Citigroup Global Services employees about 8000 people in Mumbai and Chennai. The US bank took over the BPO unit in 2004 by acquiring the 55.6% it didn't already own in the business.