The meeting is also expected to be attended by opposition leader Sharad Yadav may also attend the event. A senior Rashtriya Lok Samta Party (RLSP) leader said talks between his party and the UPA constituents are almost final and an announcement by Kushwaha on joining it is likely to be made at a press conference on Thursday.
Senior Congress leader Ahmed Patel had met Kushwaha after the latter quit the BJP-led National Democratic Alliance.
The UPA believes that Kushwaha's decision to join it will help it build momentum against the NDA in Bihar. Besides BJP, Chief Minister Nitish Kumar's JD(U) and Union minister Ram Vilas Paswan's LJP are other constituents of the NDA.
The saffron alliance had swept the Lok Sabha elections in 2014, winning 31 of the state's 40 seats.
Earlier in the state, in a series of tweets, Chirag Paswan had on Tuesday cautioned the BJP against damage to the NDA in the event of the BJP's failure to arrive at a seat-sharing formula that was respectable for other allies.
His tweets have triggered speculations that the party, which was part of the Congress-led UPA for a decade before switching over to the BJP-led coalition during the 2014 polls, was bracing for changing sides yet again.