US Ambassador Timothy Roemer will meet Home Minister P Chidambaram on Monday evening to discuss India's access to David Coleman Headley.
Sources say that India has been assured by the US Justice Department that it alone will decide whether India can quiz Headley directly about his role in 26/11 and other attacks in the country.
In a plea bargain last month, Headley accepted that he was guilty of planning and executing bombings at public places in India, including 26/11, on behalf of the Lashkar-e-Toiba (LeT).
In return, American officials agreed that the death penalty would be waived for him, and that he would not be extradited to India.
Indian intelligence officials have been given mixed signals by the US about whether they can question Headley directly. His plea bargain obliges Headley to testify in proceedings like India's 26/11 trial. However, Roemer surprised India last month by announcing that no decision had been taken on whether India could interrogate Headley directly.
Roemer's statement came after US attorney General Eric Holder phoned Chidambaram to assure him that India would get the access it wanted to Headley, a Pakistani-American who made multiple trips to India between 2006 and 2008 to survey the places that would become the sites of the 26/11 attacks in Mumbai.
Sources say that India will take a week to finalize its official written request for access to Headley, and that the Home Ministry is confident of getting access to Headley within 30 days. India's request will be sent to the US Justice Department who will then pass it on to the judge hearing the Headley case in Chicago.