The Janata Dal (United) will contest 138 seats and its ally, the Bharatiya Janata Party, 105 in the forthcoming Bihar assembly election.
Addressing a press conference in New Delhi on Monday, JD (U) chief Nitish Kumar said the two parties, however, will have separate manifestos.
Senior BJP leader Arun Jaitley was also present at the press conference.
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Nitish said the two parties will contest the assembly polls in Jharkhand also together, with the BJP contesting 63 seats and JD (U) 17.
"The two parties will campaign jointly [both in Bihar and Jharkhand]," Jaitley said.
When asked how the two parties were placed in Bihar and Jharkhand, Jaitley said: "We would get enough seats to form the government [in Bihar]. The anti-incumbency factor is so strong that it will be evident in the elections."
Both Jaitley and Nitish denied there were any differences between them on the issue of inviting Ram Vilas Paswan's Lok Janshakti Party to join the alliance.
"We had made an offer to Paswanji that he should come with us and lead the united fight against Lalu Yadav to remove him from power in the state. If he comes with us even now, he would be our chief ministerial candidate. I am not in the race. BJP and JD (U) have decided not to project anyone for the post of chief minister," Nitish said.
Senior BJP leader Sushilkumar Modi said the party is happy with seat sharing arrangement in Bihar. "Last time we got 84 seats and this time we have got 21 more. The effort is to give the people of Bihar relief from Lalu's rule," Modi said.
JD (U) president George Fernandes was conspicous by his absence at the press conference. "George is not feeling well and is undergoing treatment. He will join the poll campaign soon," Nitish said.
