"There would be a reshuffle after the monsoon session, and it is likely to take place before Independence Day on August 15," a BJP leader said.
The talk of reshuffle has gained ground after the Bharatiya Janata Party (BJP) chose its senior leader M Venkaiah Naidu as its vice-presidential candidate. The portfolios he handled - Information and Broadcasting and Housing and Urban Development - were respectively given to union ministers Smriti Irani and Narendra Singh Tomar.
Finance Minister Arun Jaitley is already holding charge of the defence ministry after Manohar Parrikar resigned to become Goa Chief Minister. Union Science and Technology Minister Harshvardhan is holding additional charge of the environment portfolio following the death of Anil Madhav Dave in May.
The Opposition has been criticising the government for not having a "full-time" defence minister amid border tensions with Pakistan and China.
BJP sources said the impending cabinet reshuffle may be large, and there could be some leaders drafted from the party into the government and vice-versa.
The strength of the Council of Ministers, including the Prime Minister, is 74 at present.
Narendra Modi took over as Prime Minister on May 26, 2014, and the first expansion of his ministry took place in November 2014.