Mining giant BHP Billiton has approved $1.2-billion pre-commitment capital for the first phase of its Olympic Dam project the first phase expansion of the Olympic Dam in South Australia.
With this, the project moves closer to board approval after the South Australian government signed off on the plans.
The miner has signed an indenture with the South Australian government for expansion of the Olympic Dam mine into the largest open cut mine in the world.
Under the agreement, BHP has guaranteed to spend at least $1.2 billion in the year following the passage of the required legislation through the state parliament, where it would be introduced on Tuesday.
The signing of the deal was the main milestone premier Mike Rann set for himself before stepping down.
According to the Greens, the decision to clear the world's largest copper and uranium mine would cause enormous harm to public health.
The Olympic Dam mine expansion has received environmental approval from the federal, South Australian and Northern Territory governments.
The mine expansion near Roxby Downs has also been approved under the Environment Protection and Biodiversity Conservation Act.