According to NCP chief Sharad Pawar, the two allies will be contesting 125 seats each in the October 21 Assembly polls and 38 seats would be left for other partners of the opposition alliance. The state has a 288-member Assembly.
"Our alliance is on We shall make the official announcement shortly," Congress General Secretary and spokesperson Sachin Sawant told .
The Congress and NCP have declared readiness in terms of seat-sharing even while the BJP and Shiv Sena have failed to resolve differences over how many seats each would be contesting.
The Shiv Sena is demanding 135 seats but the BJP is reportedly ready to part with only around 110-115 seats.
The Congress and NCP are also moving ahead on selection of candidates for the polls in which they are aiming the wrest power in the state.
The Central Election Committee of the Congress, chaired by party's interim President Sonia Gandhi, has held discussions with senior party leaders for 60 seats on September 13 at her residence.
Another meeting to discuss 65 party candidates is scheduled at her residence today.
A party source said the candidates' list will also be announced in a day or two after it is finalised by Sonia Gandhi.
According to Congress leaders, all the sitting MLAs of the party will be again repeated in the 2019 assembly polls.
Meanwhile, ahead of the Assembly polls, the Congress and the NCP have suffered major setbacks as several of their senior leaders have quit.
Senior Congress leader Kripa Shankar Singh, once billed as the Congress' benign north-Indian face in Mumbai, quit the party some days back.
Earlier, in June, senior Congress leader Radhakrishna Vikhe Patil, who was also the Leader of Opposition in the Maharashtra Assembly resigned as MLA. After him, another Congress MLA and former Minister Abdul Sattar also quit as a legislator.
Even NCP has faced desertions in the last few months. Prominent defectors included former minister and Navi Mumbai strongman Ganesh Naik, who was with the NCP for at least two decades before he joined the BJP recently.
Udayanraje Bhosale, a direct descendant of warrior king Chhatrapati Shivaji Maharaj, also resigned from his Parliamentary membership from Satara in western Maharashtra before joining the BJP recently.
Other NCP leaders, who have joined the Shiv Sena are sitting MLAs Pandurang Barora, Shivendraraje Bhosale, Avdhoot Tatkare and his father and former MLC Anil Tatkare, Dilip Sopal and former state unit president Bhaskar Jadhav.
Prominent former NCP MLAs who have joined Raj Thackeray-led Maharashtra Navnirman Sena (MNS) are Sachin Ahir and Madhukar Pichad, who had served as ministers in the erstwhile Democratic Front (DF) government in the state. Both of them were considered close to Pawar.
Meanwhile, former NCP MPs Dhananjay Mahadik and Sanjeev Naik too have joined the BJP. Those from the NCP fold who have switched their allegiance to the BJP are MLAs Sandeep Naik, Vaibhav Pichad, and Rana Jagjitsinh.
Adding to the worries on both sides are other parties which have jumped into the poll fray like Prakash Ambedkar-led Vanchit Bahjan Aghadhi (VBA) and Aam Aadmi Party (AAP).
The Hyderabad-based All India Majlis-e-Ittehadul Muslimeen (AIMIM) unilaterally snapped ties with the VBA, but Ambedkar is still optimistic that it would return to the VBA fold which will contest all 288 seats.
MNS circles claim the party may independently contest around 125 seats and is hopeful of being catapulted as a 'king-maker' in case the other alliances fail to bag majority after the elections.
AAP national spokesperson Preeti Sharma-Menon said the party plans to contest around 50 seats in the state where it has a substantial support base.
( With inputs from IANS )