Wholly owned subsidiary Cloud Peak Energy holds most of the North American coal assets of Rio Tinto Energy America – the second largest US coal producer.

Operating predominantly in the Power River Basin, Cloud Peak operates three of the five largest coal mines in the region.

Rio Tinto Energy America’s properties include the Antelope, Colowyo, Cordero Rojo, Jacobs Ranch, Spring Creek and Decker Coal mines.

Rio said a final decision on whether to pursue the IPO or to pursue another form of divestment would occur once the options had been more fully explored.

The sale of the assets has been on the table since last year when Rio released a strategic review upon its acquisition of aluminium group Alcan.