Gandhi met Singh at his residence here. She was accompanied by her political secretary Ahmed Patel.
The meeting comes a day after the Prime Minister met President Pratibha Patil.Though it was described as a routine meeting, there were indications that a re-jig of the UPA ministry was possible later this week.
Sources said that Singh may utilise the opportunity to inject fresh blood into the Cabinet.
Ministers like Sharad Pawar and Kapil Sibal are holding more than one portfolio and are likely to shed some of them.
There are some vacancies including that created by the resignation of A Raja, Prithviraj Chavan and Shashi Tharoor.
The feeling in the Congress was that major portfolios like Finance, Home, Defence and External Affairs may not be disturbed in the proposed exercise which is mainly aimed at filling up the vacancies.
Pawar, who holds Agriculture, Food and Consumer Affairs Ministries, has earlier expressed his intention to shed some of his burden.
Similarly, Sibal who has the charge of HRD, Telecom and Science and Technology, may shed Science and Technology.
He is said to be passionate about retaining HRD in which he has initiated certain reforms and would like to pursue them.
He is unlikely to be disturbed from Telecom which was given to him after Raja`s resignation in the wake of 2G spectrum allocation scam.
Union Ministers C P Joshi (Rural Development) and Vilasrao Deshmukh (Heavy Industry) may be drafted for party work.
DMK, which has a vacancy in the Cabinet after Raja`s exit, may get a berth. The name of T R Baalu, a former minister, is among those mentioned from the party as a replacement for Raja.
Sudip Bandhopadhyay, a Trinamool Congress leader, may get a berth as a representative of the largest constituent after Congress in the UPA.
There has been no representation to three states in the Union ministry -- Chhattisgarh, Goa and Manipur.
Gandhi had detailed deliberations with Singh more than twice in the last week, apparently to plan out the exercise, which would be the first after the UPA-II came to power in May 2009.