The impression was given by American officials to a team of Indian investigators who has visited the US early this month.
"There is progress in the discussion with the US officials. Hopefully we will get access to them soon," a home ministry official said.
Request to interrogate Headley's wife Shazia Gilani, his girlfriend Portia Peter, one more female friend and Rana was given by Home Secretary R K Singh to his US counterpart Jane Holl Lute during the third Indo-US strategic dialogue held in Washington in June.
India had access to 50-year-old Pakistani-American Headley, who had carried out a recce of the 26/11 Mumbai terror attack targets for the LeT, but so far had not been able to quiz his Pakistani-Canadian businessman friend Rana, wife Shazia and the two girlfriends.
Indian investigators into the 26/11 case believe that Rana, Shazia and others have a lot of information and through their interrogations more light may be thrown on the conspiracy hatched to carry out the worst terrorist strike in India and role of those behind it.
Headley had pleaded guilty to 12 terrorism charges, including his involvement in the November 2008 terrorist attacks in Mumbai that claimed 166 lives. He had, however, entered into plea bargain with US authorities.