The firm is aiming to raise between $150m and $200m from the stake sale, up to double the $100m it paid for the stake in 2009, a source with knowledge of the deal told Reuters.
A second source said a formal process had been launched but the company had not decided wether to run the sale through secondary deals or by targeting a strategic buyer.
The news comes in the same week it emerged private equity-backed telecoms company Bharti Infratel was to sell a stake in its satellite television unit Bharti Telemedia.
The divestment is part of a wider programme which will see the company, which is the telecom tower unit of Indian mobile phone carrier Bharti Airtel, partially exiting non-telecommunications businesses, the Wall Street Journal said.
Private equity investors including KKR, Macquarie, Citigroup, Investment Corporation of Dubai and AIF Capital own a combined 13 per cent stake.
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