"It is unfortunate that the PM has not confirmed an appointment with the delegation," ruling JD(U) spokesman Sanjay Singh told reporters.
Both JD(U) and Chief Minister Nitish Kumar had sought an appointment with the prime minister on the issue on several occasions but no response was received, he said.
"The delegation is ready to submit a memorandum to the PM on July 13 in support of the demand ... We hope to get a positive response."
Kumar had yesterday flagged off altogether 26 vehicles - an air conditioned rath and other vehicles carrying over 1.25 crore signatures of the people of Bihar to be sibmitted to the prime minister.
The 121-member delegation includes Bihar JD(U) president Vashisth Narayan Singh, MPs R C P Singh and Monazir Hasan, a number of MLAs and leaders of various fronts of the ruling party.