PATNA: A 'grand alliance' at the centre was RJD chief Lalu Prasad's birthday wish today as greetings poured in from Congress president Sonia Gandhi , West Bengal Chief Minister Mamata Banerjee , her Bihar counterpart Nitish Kumar and other leader."Delhi will now see the leadership of mahagathbandhan . All coalition partners should start preparations," Prasad, who turned 70, tweeted after Bihar Congress chief and state education minister Ashok Chaudhary wished him.The RJD chief also reminded Trinamool Congress chief Mamata Banerjee that they stand in solidarity for the "great cause ahead" after she extended greetings to him.Ever since a Nitish-led 'mahagathbandhan' (grand alliance) of RJD, JD(U) and Congress handed down a stunning defeat to BJP in 2015 Bihar Assembly election, a grand alliance is being seen as the only way to stop the saffron juggernaut.Nitish drove to 10, Circular Road, where the RJD supremo lives in the official residence alloted to his wife Rabri Devi, and gave a bouquet to Prasad before the two embraced each other.Speaking to reporters, Kumar said : "Lalu Prasad has made notable contributions to Bihar politics and our society."The Bihar chief minister again greeted the RJD supremo after dedicating two bridges, Sonepur-Digha and Ara-Chapra, to the people and said that what could be a better occasion to do so than the birthday of Lalu Prasad.Congress president Sonia Gandhi and Union Minister Giriraj Singh also greeted Lalu Prasad on his birthday."Sonia jee has spoke to me on telephone to wish me happy birth day," a beaming RJD supremo told reporters.In between his busy schedule, Lalu Prasad took time out to cut a 70-pound cake at his residence in the presence of his wife, Chaudhary and a host of ministers, leaders and workers of the RJD and other allies of the grand alliance.While attempts to forge a grand alliance in Uttar Pradesh fizzled out, the upcoming Presidential election has seen fresh moves for opposition unity against the BJP.