NEW DELHI: Tata Teleservices' telecoms tower joint-venture has not yet begun due diligence to buy some or all of unlisted Aircel's tower holdings, its managing director said on Tuesday.

"Things are going slow," Anil Sardana told reporters at a news conference,

Tata Teleservices, India's sixth-largest mobile operator, owns 51 percent in Tata Quippo, the joint venture. Japan's NTT DoCoMoowns a 26 percent stake in Tata Teleservices.

Banking sources had told Reuters last month Aircel had shortlisted American Tower, Bharti Infratel, Crown Castle and Tata-Quippo for due diligence.