Firms have to submit bids by Dec. 21 for a total of 71 blocks of spectrum put up for auction across 20 of India's 22 telecoms zones, according to a memorandum to prospective bidders.
The government did not give a reason for the second extension.
The base price for 3G spectrum across the country is 35 billion rupees ($750 million), and Telecoms Minister Andimuthu Raja has said the government would net at least 250 billion rupees from the sale.