The 'Panel of Experts' was initially supposed to submit its report by December 15.
"The (period of) the submissions to the panel has been extended to the end of this year, from the previous deadline of mid-December," said Farhan Haq, the Deputy Spokesman of the Secretary General.
"They are on track to put out a report on their schedule. I don't have a precise date for when that will happen," Haq said in response to a question at the daily noon briefing held at the UN headquarters in New York.
Haq said the Secretary-General has made it clear that he would review whatever the panel gives him and then decide at that point about making anything public.
Last week, Ban said that his panel of experts would now be able to visit Sri Lanka and meet a Sri Lankan commission looking into the ethnic conflict that ended last May.
"I sincerely hope that the Panel of Experts will be able to have good cooperation, to have an accountability process and make progress as soon as possible. This is a result of long consultations, and I appreciate the flexibility of the President (Mahinda) Rajapaksa on this issue," Ban had said.
Lanka said earlier that it would not allow the panel to visit the country, calling it an infringement of its sovereignty.
Three international non governmental organisations, the New York-based Human Rights Watch, London-based Amnesty International and Brussels-based International Crisis Group have snubbed an invitation to appear before the Commission on Lessons Learnt and Reconciliation, last month, accusing it of a cover-up and lacking credibility.
Both the Tamil Tigers and Sri Lanka's government have been accused by human rights groups of committing crimes against humanity during the last phase of the three-decade- long conflict that ended in May 2009.