Rio Tinto said that it has 10 million tonnes of thermal coal is held up by infrastructure bottlenecks in the New South Wales Hunter Valley and Queensland. It added that infrastructure constraints have had a big impact on its Bengalla mine near Muswellbrook, as well as its Mount Thorley Walkworth and Hunter Valley Operations, near Singleton.

The Blair Athol mine has also felt the effects from bottlenecks in Queensland's port and rail systems. But Rio Tinto is confident the constraints will be removed once infrastructure improvements come on line, such as Newcastle's third coal loader and the expansion of Port Waratah coal services facilities.

It hopes to double its Australian thermal coal production by 2015 and in the same period increase production at its Hunter Valley operations to 24 million tonnes per year.