Patna, Aug 6 : In a bid to corner the BJP, Bihar Chief Minister Nitish Kumar has written to Prime Minister Narendra Modi, reiterating the demand for a caste-based census in the state. While interacting with reporters on Thursday, he said that he has sent a letter to the PM, urging him to give time so that members of all parties of Bihar can meet him and share their views on the issue. Leader of Opposition Tejashwi Yadav had, during the Monsoon session, met Nitish Kumar, and requested him to fix an appointment with Modi for the purpose. Sources say that the friction between ruling allies, the Janata Dal-United and the Bharatiya Janata Party has intensified in the last few weeks, especially after the recent cabinet expansion of the Modi government. Both JD-U and BJP leaders are taking potshots at each other to take the upper hand in Bihar. Recently, JD-U parliamentary board President Upendra Kushwaha declared Nitish Kumar as PM material, drawing a retort from BJP minister Samrat Chaudhary, who said that there is no vacancy of the Prime Minister's post in the NDA. He further said that running a four-party coalition government in Bihar is extremely difficult as all the parties have different ideologies. Even Nitish Kumar responded to his minister's statement, saying that he saw no problem in running a coalition government, and if Chaudhary has any problem, he should talk to his party's leaders. /IANS