The first expansion and reshuffle of the three-tier ministry will take place at the Rashtrapati Bhavan at 1 p.m.
The exercise could also give greater representation to some allies of the Bharatiya Janata Party, including the Shiv Sena, with which relations remain strained in the wake of the Maharashtra elections.
The Sunday event will happen before the start of parliament's winter session Nov 24.
Goa Chief Minister Manohar Parrikar, who is slated to be inducted as the defence minister, said Friday that he will resign Saturday.
Parrikar told reporters in Panaji that a new chief minister will be sworn in Saturday afternoon.
BJP sources said Parrikar may be inducted into the Rajya Sabha from Uttar Pradesh, from where the party has 71 of the 80 Lok Sabha members.
Informed sources said two more representatives from the Shiv Sena could be inducted into the Modi ministry despite the logjam over the party's participation in the BJP-led Maharashtra government.
A Sena leader made light of the new induction, saying the BJP was merely implementing its earlier promise to induct two more Sena nominees in the Modi government.
"(Our joining) would depend on whether the offer is for cabinet, minister of state or independent charge," the leader told IANS requesting anonymity.
The Sena now has one minister in the Modi government, Industry Minister Anant Geete.
With the BJP making no announcement, the widespread feeling is that Modi would like to make his government more broad-based vis-a-vis the geographical spread.
New ministers may be taken from Rajasthan, Uttarakhand, Delhi, Uttar Pradesh and Bihar besides Haryana and Maharashtra -- two states where the BJP was elected to power for the first time last month.
Among those most likely to be inducted are BJP vice president Mukhtar Abbas Naqvi and party general secretary J.P. Nadda, an old associate of the prime minister.
The sources said BJP MPs Giriraj Singh and Jayant Sinha may also get portfolios. The party may also induct Birender Singh, who joined the BJP before the Haryana polls after quitting the Congress.
The Modi government now has 22 cabinet members and 22 ministers of state, some holding independent charge.
Many ministers, including Arun Jaitley, Nitin Gadkari, Prakash Javadekar, Nirmala Sitharaman and Piyush Goyal, hold multiple ministries.
With Modi repeatedly emphasising that his government will work on the mantra of "minimum government, maximum governance", the size of the union council of ministers is not expected to be large.