The mining giant said US$7.4 billion will be pumped into continuing production growth in the company's Western Australia iron ore operations to expand capacity to more than 220 million tonnes a year.

Of that, US$3.4 billion will be used to develop its Jimblebar mine and rail links, and to buy mining equipment and rolling stock.

Another US$2.3 billion is earmarked for improvements to Port Hedland, including additional berths and ship loaders, a car dumper, rail works and rolling stock.

The rest of the investment will be used to improve port blending facilities to expand the life of the resource.

The Melbourne-based miner also announced a US$5 billion cash injection into three key metallurgical coal projects in Queensland's Bowen Basin.

Another US$400 million will be used to expand a thermal coal mine in the New South Wales Hunter Valley.