Noting that there was "enthusiasm" on part of Pakistan leadership to see Singh visiting that country, the source said, "We are receiving some interesting positive signals but at the same time there are expectations that remain unfulfilled."
Asserting that "this is not a pre-conditional approach", the source said, "there are things that have hurt us very gravely and that sense of hurt is yet not over".
"We owe it to our people that we have not forgotten it," he said, referring to the 2008 Mumbai carnage in which 166 persons were killed.
"Whether we are bitter, the answer is no. Whether we have forgotten, the answer is no. Therefore, a little balm is necessary even to give us the strength and courage to move forward and that is all we expect from Pakistan.
"There must be some delivery. We are ready for some delivery, so that we can move forward and all this has to be kept in mind when the Prime Minister decides what the path will be," he said.
Reports emerging from Pakistan in the last one month have indicated that government there was keen on Singh's visit before their general elections in March. According to these reports, Singh's birthplace Gah was also being spruced up for a possible visit by him.
He also mentioned that there was a very "small window" given that Pakistan was fast moving towards their elections.
"The window is very small because they are moving very fast towards their elections next, I am not very sure that the visit of that nature is possible and probable during that window which is very short."
He also made it very clear that "accountability for what happened in the past and assurance for what must not happen in future" should go hand in hand.
The source also said that India was putting best efforts which were "persistent, consistent, clear and determined" to push Pakistan on 26/11.
"We are cautiously moving forward and we hope that they will continue to give indication that our cautious movement forward is a correct movement forward," the source said, while noting that a lot of factors have to be taken into account before a prime ministerial visit to Pakistan takes place.
During his meeting with Pakistan President Asif Ali Zardari on the sidelines of the NAM summit in Tehran in August, Singh had conveyed that expeditious concluding of 26/11 trial would be the biggest confidence building measure by Pakistan.
The source also said though India welcomes forward movements in some areas. At the same time, the matters placed on the agenda must be clear one by one.
On JuD Chief Hafiz Saeed, the mastermind behind 26/11, still moving freely in Pakistan, the source said there are issues about engagements on the wish list that India has given and there was a need to move forward on that before one can show any "further willingness to move forward. There are things on which you cannot do things in haste."
On operationalising the visa pact, which was signed during former External Affairs Minister S M Krishna's visit to Islamabad in September, the source said there was no delay and follow up steps were being taken.