They said a majority of the UPA allies, including the Left parties, favour Mukherjee, the External Affairs Minister, while a section of Congress want Patil in the top post citing Mukherjee's "indispensability" in organisational, legal and administrative affairs.
Finalisation of the candidate is expected only next week after Tamil Nadu Chief Minister and Dravida Munnethra Kazhagam chief M Karunanidhi holds consults UPA leaders in New Delhi, said the sources.
Besides Patil and Mukherjee, other senior Congress leaders in contention for the post are Sushil Kumar Shinde, Karan Singh and Motilal Vora.