State-run Coal India (CIL) is planning to submit a bid next month to buy a 40% stake in Indonesia-based golden energy Mines for an estimated $1bn.

CIL is in the process of completing the due diligence report on the Golden Energy asset, which consists of ten coal mining areas in Indonesia, including those in Sumatra and Kalimantan islands, with total estimated coal reserves of 400Mt.

The Indonesian mining company plans to raise its output to ten million tons this year and plans to produce 15 million tons in 2014.

The Indian government sold a 10% stake in CIL last year for $3.4bn in an initial public offering, according to Reuters.