Rio Tinto Ltd/Plc said that the company is planning to invest $793 million to extend the Kestrel coal mine in Australia, as it looks to internal growth to fight off an approach from its rival BHP Billiton, Reuters reported.

According to the statement, the total cost of the work at the Kestrel mine in the coal-rich Bowen Basin region of Queensland state, aimed at increasing productivity when existing sections of the mine start showing signs of depletion in about four years, was $991 million.

Rio holds an 80 percent stake in the mine. Mitsui Kestrel Coal Investment, which is owned by Japan’s Mitsui Group holds the other 20 percent. The work will allow for annual production of around 5.7 million tons of coal until 2031, Rio said.

The work will provide access to 112 million tonnes of high quality hard and semi-hard coking and thermal coal for export, it added.

So far this year, Rio Tinto has spent $44 billion on new projects, including its $38.1 billion acquisition of Alcan in October