Indian government had placed the money in the Pentagon-managed account for purchase of weaponry under the Foreign Military Sales (FMS) program from US vendors like Boeing and Lockheed Martin.
Defence Minister Manohar Parrikar said at a press conference - "Because of ill-management, or lack of attention to this account, we had slightly less than $3 billion which is piled up in this account, which was not earning any interest. It was just lying there in the account."

Manohar Parrikar with Narendra Modi, 2014. Source: wikimedia.commons.org
Parrikar further added - "From somewhere near $3 billion, the account has come down to $1.7-1.8 billion. During last year, we must have paid nearly Rs 6,000 crore from this fund for our committed liabilities…. We have saved almost $700-800 million in foreign exchange."
The current year's budget had revised allocations that brought down the capital expenditure to Rs 65,808 crore, while the coming year's capital budget for the three services amounts to Rs 70,380 crore.
So, even if Parrikar saved Rs 9,000 crore, it still leaves Rs 3,000 crore underspent!