According to a news channel report, the leaders of both the parties ended the deadlock over seat-sharing by reaching the consensus.
However, the formal announcement will be made shortly to announce the seat-sharing and alliance for the October 15 state assembly elections.
The leaders of Shiv Sena, BJP and other allies of the grand alliance will be present at the crucial meet.
Earlier in the day, Sena group leader in Assembly Subhash Desai, party spokesperson and Rajya Sabha member Sanjay Raut arrived at the BJP office - Vasant Smriti Bhavan- in Dadar in central Mumbai around noon and met top BJP leaders on the alliance issue.
BJP's Maharashtra poll in-charge Om Mathur and state party president Devendra Fadnavis were among those present at the meeting.
Fadnavis has convened a meeting of state BJP unit functionaries, district unit presidents, legislators and MPs here today to discuss the political situation ahead of the Assembly polls.
Leader of Opposition in Assembly Eknath Khadse and Leader of Opposition in Council Vinod Tawde are also participating in the meeting.
BJP has already rejected the formula put forth by Sena chief Uddhav Thackeray of his party contesting 151, BJP-119 and allies 18 seats for the elections to the 288-member state Assembly.
BJP on Monday made a counter offer seeking 130, a climbdown from earlier 135, but said it would contest all 288 seats if "compelled" to part ways from its oldest ally in the NDA.
(With PTI inputs)