The FBI said Headley attended militant training camps in Pakistan
India says it will ask the US for access to a Chicago man who has pleaded guilty to scouting targets for the 2008 attacks on the city of Mumbai.
Home Minister Palaniappan Chidambaram said India welcomed the guilty plea entered by David Coleman Headley.
On Thursday, Headley pleaded guilty on 12 counts in a Chicago court. More than 170 people died in the Mumbai attacks.
He also admitted plotting to attack a Danish newspaper that published a cartoon many Muslims deemed offensive.
Headley, 49, had denied the charges but changed his plea to avoid the death penalty or extradition to India, Pakistan or Denmark.
"We will continue to press our request for access to interrogate him [Headley]," Mr Chidambaram told reporters in the Indian capital, Delhi.
"There are many more questions that we want to ask, much more information that we wish to get," he added.
Mr Chidambaram said he had seen a copy of the plea agreement and that Mr Headley could face life imprisonment which would satisfy India.
He also said the US had shared a significant amount of information emerging from Mr Headley's interrogation which is helping India's investigation into the Mumbai attacks.
In changing his plea in the Chicago court, Headley admitted 12 counts of conspiracy.
Prosecutors will therefore ask for a lesser sentence, but US District Court Judge Harry Leinenweber said Headley could still be jailed for life.
Born in 1960 in the US to a Pakistani father and an American mother
Spent much of his childhood in Pakistan
Attended a military boarding school in Islamabad
Dropped out of school at 17
Joined his mother in the US after she divorced his father
Changed his name to David Headley in 2006
Made five extended trips to Mumbai between 2006 and 2008
FBI says he took pictures and made videotapes of various targets, including those attacked in 2008
Arrested in Chicago on 3 October 2009 as he was about to travel to Pakistan
Prosecutors said Headley, a Pakistani-American, had made several surveillance trips to India and Denmark.
According to court documents, he passed on information to his contacts with the Pakistan-based Islamic militant group, Lashkar-e-Taiba.
The group has been blamed for organising the Mumbai attacks.
Headley was arrested by FBI agents in Chicago in October while trying to board a plane for Philadelphia.
He is alleged to have told prosecutors that he had been working with Lashkar-e-Taiba since 2002.
He was first charged with plotting to attack the Danish newspaper Jyllands-Posten after they angered Muslims by publishing cartoons of the Prophet Mohammed.
Headley changed his name from Daood Gilani in 2006 after he was told by members of Lashkar-e-Taiba that he would be travelling to India to carry out surveillance duties for the group, prosecutors said.