Manmohan Singh, the Indian prime minister, has urged fair treatment for Bharti Airtel, one of India’s biggest mobile operators, in its negotiations with South Africa’s MTN over a $23bn cash and shares merger as the deadline to conclude the deal approaches.

Mr Singh raised the deal with Jacob Zuma, South African president, at the G20 summit in Pittsburgh at the weekend amid concerns in India that the South African government is seeking to delay or even block the deal out of nationalist considerations.