Defending the 'lenient' sentence, US Secretary of State Hillary Clinton said Headley had yielded significant information to help India and the US prevent Mumbai-like attacks in future.
"I think it is unfinished business that we are not in any way walking away from. I'm leaving office, but I can assure you and the Indian people this remains one of our very highest priorities," Clinton said when asked if she was satisfied with the success that she had in bringing the perpetrators of 26/11 to justice during her tenure.
Clinton, 65, who is set to leave the State Department on February 1, was interacting with global audiences at a farewell talk through a satellite link.
"A lot of useful information was obtained. And I think that this sentence represents both the punishment that he (Headley) richly deserves for his participation but also a recognition of the role that he has played and is expected to continue to play in supporting Indian and American efforts to prevent the kind of horrific attack that occurred in Mumbai," she said while responding to an Indian journalist's query on bringing to justice the perpetrators of 26/11.
The sentence for Headley for his role in plotting the Mumbai attack of 2008 left India majorly disappointed.
Under the plea bargain agreement Headley reached with the US government, he could have been sentenced to a life in prison, but the prosecutors only sought a maximum of 35 years for the rogue DEA agent, leaving a slight possibility that the 52-year-old might walk out of prison.
India had pressed for extradition of Headley but that too was ruled out after the LeT operative agreed to cooperate with the US agencies.
Clinton said Headley had undergone an intensive amount of investigation and interrogation by both Indian as well as American authorities.
She also reminded Pakistan of the need to take action against militants operating from its soil.
"We were successful in capturing and eliminating a number of the most dangerous terrorists who have safe haven inside Pakistan. We have continued to press the Pakistani government because of course, the terrorists inside Pakistan are first and foremost an ongoing threat to the stability of Pakistan, and they need to deal with it because of that as well as the implications for India, Afghanistan, the United States and elsewhere," she said.
She also commended efforts by the Indian and Pakistani leadership in restoring bilateral ties, and said this will help create a better environment of cooperation.
"I also think that the efforts that both Prime Minister (Manmohan) Singh and President (Asif Ali) Zardari in Pakistan have made to improve communication, business, trade, commerce between India and Pakistan helps to create a more receptive environment for dealing with these serious threats," she said.
"So of course I'm not satisfied. I believe going after terrorism is an obligation of every country everywhere, every sensible person. We can have disagreements, but they cannot be in any way using violence or condoning the use of violence," Clinton said.
"We are not giving up. We are on this job literally every single day. We have improved our information-sharing, our law enforcement cooperation with India. I think that will pay dividends in years to come," said Clinton, who is making way for John Kerry.
The interaction included questions from a select six prominent news channels from across the world. This was Clinton's 59th town hall, three of which were held in India.