The theme of the reshuffle is to fulfill Modi's earlier promise of 'maximum governance, minimum government.'
Some key ministries are likely to be merged.
Archis Mohan, Nivedita Mookerji, Sanjeeb Mukherjee report.
A reshuffle and expansion, set to alter the complexion of the Narendra D Modi-led council of ministers, is expected on Sunday, September 3.
The overarching theme of the reshuffle is to fulfill the PM's earlier promise of providing maximum governance with minimum government.
Some of the key ministries are likely to be merged.
It would entail, sources said, setting up omnibus integrated ministries for sectors like transport and infrastructure, agriculture, energy and industry.
The reshuffle would impact over two dozen ministries.
Each such omnibus ministry would have a Cabinet minister at the top, with several ministers of state responsible for different sectors.
One of the proposals is to have one mega ministry for agriculture, fertilisers, and panchayati raj.
Another proposal is to integrate transport and infrastructure-related ministries.
Sources said that with most of the crucial assembly polls out of the way, the government is keen to show intent about delivering upon its promise of economic growth made in 2014 and shape the narrative that would help the Modi government score an encore in the 2019 Lok Sabha polls.
By Friday night, seven ministers had submitted their resignations. Another six had been asked to quit.
"We offered our resignations to help the PM with a free hand in the reshuffle," a Cabinet minister who quit on Friday said. The minister did not want to be named.
Ministers making their debut, and those likely to be promoted to Cabinet rank, are to be administered the oath of office after 10 am on Sunday.
The PM leaves on Sunday afternoon for China to attend the BRICS summit and would subsequently travel to Myanmar for his first State visit to that country.
Bharatiya Janata Party President Amit A Shah met the PM on Thursday evening to discuss the reshuffle.
On Friday, Shah attended the opening day of the three-day annual meeting of the Rashtriya Swayamsevak Sangh and its allies. Shah also held consultations with RSS Sarsanghchalak Mohan Bhagwat on the Cabinet reshuffle.
In his opening remarks at the meeting, a top RSS leader noted that any ideology faces three stages, that of indifference, opposition and acceptance. The RSS, the leader said, has overcome the first two stages and is now experiencing acceptance in society.
While several ministers met the PM on Friday evening, senior ministers Sushma Swaraj, Arun Jaitley and Nitin Gadkari met at Home Minister Rajnath Singh's home to discuss the contours of the Cabinet reshuffle.
In a related development, Rajasthan Chief Minister Vasundhara Raje, who was in the capital, visited the Prime Minister's Office. Sources in her office said she did not meet Modi.
The ministers who had quit by Friday evening were Ministers of State Rajiv Pratap Rudy, Sanjeev Kumar Balyan, Faggan Singh Kulaste, Mahendra Nath Pandey and Bandaru Dattatreya.
Rudy and Dattatreya were ministers of state with independent charge. Rudy said he quit under instructions from the party.
Sources said Cabinet Minister Kalraj Mishra also submitted his resignation while his Cabinet colleague Uma Bharti has been asked to follow suit.
While the five junior ministers will be drafted for party work, Mishra and Bharti could get posted as governors.
Bharti has protested and expressed her unwillingness to move to a Raj Bhavan.
Apart from reinvigorating the council of ministers, the reshuffle has set out to get some of the talent back to the party.
Some ministers who proved to be effective spokespersons when the BJP was in the Opposition have been asked to return to party work.
Performing ministers like Piyush Goyal could be promoted to Cabinet rank.
Ministers handling more than two portfolios could find their workloads reduced. These include Jaitley, Harsh Vardhan, Smriti Irani and Ravi Shankar Prasad.
The BJP leadership, preparing for the eventuality of falling short of the majority mark in the next Lok Sabha polls, is also keen to cement its alliances by giving more representation to its allies.
The Janata Dal-United is set to get a look in, while allies such as the Shiv Sena and the Telugu Desam Party could get better representation.
As things stand, the All India Anna Dravida Munnetra Kazhagam might have to wait to join the government.
From the BJP, those slated to debut in the council of ministers are party General Secretary Bhupendra Yadav, Vice-President Vinay Sahasrabuddhe, Madhya Pradesh leader Prahlad Patel, Karnataka unit chief Prahlad Joshi, Lok Sabha member from Uttar Pradesh and former Mumbai police commissioner Satyapal Saingh, Karnataka Lingayat leader Suresh Angadi and Shobha Karandlaje.
Karnataka is scheduled for assembly elections by May 2018.
Party sources rejected inferences that those asked to quit were considered non-performers.
Sanjeev Balyan, a Jat leader from western UP, is seen as somebody needed by the party at a time when Jats in Haryana and western UP are turning away from the BJP.
Pandey is now the BJP's UP state unit chief, Kulaste is needed in Madhya Pradesh's tribal belt and Dattatreya for party work in Andhra Pradesh and Telangana.
Rudy proved his organisational skills in the Maharashtra assembly polls in August-September 2014, and has been in charge of the party's units in southern states.
Bharti refused to confirm she had quit. She is the minister for water resources and Ganga rejuvenation.
'The media sought my reaction on reports in circulation since yesterday (Thursday). I have said that I have not heard the question, will not hear nor will I answer it. Only BJP chief Amit Shah should answer these questions,' she told the media.
From the JD-U, R C P Singh and Santosh Kumar could get ministerial berths.
Road, Transport and Highways Minister Nitin Gadkari could get more responsibilities.
Civil Aviation Minister Ashok Gajapathi Raju could be allocated another portfolio as could Railway Minister Suresh Prabhu, who has already offered to quit.
The current strength of the council of ministers, including the PM, is 73.
According to the Constitution, the limit cannot exceed 15 per cent of the total strength of the Lok Sabha.
In a 545-member House, the Union council cannot have more than 81 ministers.
This will be the third reshuffle of the Union ministry, and possibly the last before the 2019 Lok Sabha polls.
IMAGE: The last ministerial reshuffle took place on July 5, 2016. Photograph: Press Information Bureau