The decision was taken at a meeting of RJD Legislature Party at former Chief Minister Rabri Devi's residence.
RJD Legislature party leader Abdul Bari Siddiqui told reporters that the meeting has been adjourned till 3 pm tomorrow.
"RJD MLAs will meet again at 3 pm at the same venue tomorrow and party President Lalu Prasad will take a final decision on Thursday's voting for the two seats," he said.
17 out of 21 RJD MLAs attended the meeting in presence of Lalu Prasad. Four MLAs - Dinesh Kumar Singh, Kedar Singh, Anirudh Yadav and Raghvendra Pratap Singh - did not attend due to some personal problems.
RJD holds key to results of the two seats which is witnessing stiff competition between JD(U) official candidates and two Independents backed by rebels and BJP.
Considering the fact, former Chief Minister Nitish Kumar had dialled Prasad last Friday and appealed for support to JD(U) nominees to foil BJP's design to topple Jitan Ram Manjhi government and thrust an early election on the state.