Kakodkar's strong statement came on a day when Left parties said they would vote against the UPA government in Parliament in case of a confidence motion if it took the next step to operationalise the deal.

"Here is a chance ... without compromising on our principles, we can bridge energy security for the future," Kakodkar said in a public lecture on "Evolving Indian nuclear programme: Rationale and perspectives", organised by the Indian Academy of Sciences.

Without mentioning the deal but giving enough indications that he exactly meant that, he said: "If we don't do now, history will not forgive us". He termed it (the deal) one of the most promising and viable way of bridging energy security for the future.

Later, responding to reporters` queries on time-line for approaching the IAEA for a safeguards agreement and if the deal can be wrapped up year-end, Kakodkar said: "Sooner the better. But everything is not in my hands, know?. But things are not in my hands".

Earlier, he declined to comment on the raging political debate over the nuclear deal when an audience member posed a question. "That's part of politics; I don't get into politics".

On "this question why there is a hurry (in clinching the deal)", Kakodkar said, "If do it in 2020, there will be a ten-year delay".

He stressed that "we have not realised the energy gap that we face", adding, "we must maximise our options". Kakodkar said Department of Atomic Energy is making "heroic" efforts to develop uranium mines but pointed out that there are time delays (which are generally 8-9 years) because of public debate and clearances give by state governments.