DBS and Citi declined to comment.
The sources, who spoke on condition of anonymity as they were not authorised to speak to the media, did not provide any further details.
The Wall Street Journal reported this month that the sale could be valued at up to $2.2 billion.
Citi announced last year that it would exit retail operations in 10 markets in Asia as it refocuses on its more lucrative institutional and wealth management businesses.
This month, Citi struck a deal to sell its consumer business in four Southeast Asian markets to United Overseas Bank for about S$5 billion ($3.7 billion).
(Reporting by Emily Chan and Jennifer Yang; Additional reporting by Anshuman Daga in Singapore; writing by Ben Blanchard; editing by Jason Neely)
