Kumar, who was in Delhi, sent JD(U) president Sharad Yadav for talks with Lalu and Samajwadi Party chief Mulayam Singh Yadav, who has been designated as the leader of the proposed entity after a formal merger of six 'Janata Parivar' outfits.
Kumar's aides said he had undergone a minor eye surgery and advised rest.
Sources said Prasad, instead of focusing on a merger between RJD and JD(U), talked about forming a 'grand alliance' against BJP that would include all non-NDA parties, including the Left, something that would not go down well with Nitish Kumar.
Despite JD(U) yesterday deprecating any move to forge ties with Manjhi, who was ousted and replaced by Kumar after he refused to step down as Chief Minister, Lalu's insistence on his inclusion in the alliance is being seen as an attempt at procrastination.
JD(U), on the other hand, wants Lalu to back Kumar as the chief ministerial face of the merged entity.
