India's foreign minister said Friday that the US planner of the deadly 2008 Mumbai attacks should have got a harsher sentence than 35 years in prison and added that New Delhi still wanted his extradition.

David Headley, 52, who admitted to scouting targets for the Mumbai attacks in which 166 people died, cooperated with US authorities to avoid the death penalty during his sentencing in Chicago on Thursday.

"If we would have tried him, we would have sought much more (punishment). But the judge is bound by the structured system of justice delivery in the US," Foreign Minister Salman Khurshid told India's CNN-IBN TV network.

"It's a beginning," Khurshid told other reporters in New Delhi.

"This should go a long way in hopefully conveying a very clear message" that such acts are not tolerated, he added.

Last November, India executed 25-year-old Pakistani-born Mohammed Ajmal Kasab, the sole surviving gunman from the Mumbai rampage that lasted three days and traumatised India.

On the thorny issue of Headley's extradition, Khurshid said India has been "consistently" pushing its demand with Washington.

US prosecutors agreed not to extradite Headley in exchange for his cooperation after his 2009 arrest in Chicago as he was about to board a flight to Pakistan.

US authorities told the court that Headley cooperated with authorities and provided valuable details about the Pakistan-based militant group Lashkar-e-Taiba, which is blamed for orchestrating the attacks.

In delivering the sentence, US judge Harry Leinenweber made it clear he would have rather imposed the death penalty, but said the 35-year term he gave Headley would keep him "under lock and key for the rest of his natural life".