In a message to the family, he said, "A real tribute to her will be to ensure maximum punishment to the culprits.
"I pledge to work to strengthen the laws and ensure that such an incident never gets repeated again," he said.
The girl, who was gangraped and brutally assaulted by six men in a moving bus in south Delhi, died in a Singapore hospital early on Saturday morning after battling for life for her past 13 days.