The decision came after the senior-most leaders of the Congress Working Committee, headed by Congress president Sonia Gandhi, met on Thursday evening.
According to the sources, the decision came after Sonia Gandhi opposed to the popular demand from inside the party, to declare Rahul as the party's PM nominee.
However, the 43-year-old leader will lead the party's election campaign. Rahul has been entrusted the tough task of taking on Narendra Modi, Bharat Janata Party's PM candidate.
The decision will be formally announced at the conclave tomorrow to be attended by thousands of party workers.
Rahul had earlier said that he will accept whatever responsibility is conferred upon him by the party.This had led to wide speculations that he will be Congress' prime ministerial candidate.