According to a report by UK paper the Telegraph, investment bank Credit Suisse has been appointed to find a buyer for the assets.

The divestment is part of Rio's plan to slim itself down following the acquisition of Alcan last year.

The paper said Rio will only sell its coal assets with reserves that are too small for it to mine cost effectively.

Rio's coal operations in Australia include Bengalla, Blair Athol, Clermont, Hail Creek, Hunter Valley Operations, Kestrel, Mount Pleasant, Mount Thorley, Tarong and Warkworth.

North American mines include Antelope, Codero Rojo, Colowyo, Jacobs Ranch and Spring Creek.