The South Australian Government has given BHP Billiton more time to expand its Olympic Dam mine in the outback.
Announcing the extension of an indenture agreement at a news conference alongside BHP CEO Marius Kloppers, SA Premier Jay Weatherill expressed hopes for the future of the mining project, which was mothballed last August.
Mr Weatherill said granting the extension would put BHP in the best possible position to go ahead with a redevelopment as soon as it was possible.
"There is no doubt that this is a world-class ore body.
There's also no doubt that they want to develop this resource," the Premier said.
"There's also no doubt they're applying the resources to put themselves in a position to do that.
"What he (Marius Kloppers) can't do of course is guarantee anything because we're talking about a time period in the future that's contingent on a number of events occurring." BHP Billiton gave a commitment to spend $650 million over the next four years in South Australia.
It said it would spend $540 million re-scoping the expansion and another $110 million on mine research and community initiatives.
The indenture had been due to expire in the middle of December but the company now has almost four years longer to determine its plans for the area near Roxby Downs.
The extension until October 2016 gives the mining company more breathing space to plan conversion of its big outback uranium, gold and copper underground mine to a vast open pit operation, a project expected to cost about $30 billion.
Mr Kloppers said the company was keen approve a redevelopment of Olympic Dam but at this stage could not guarantee it will happen, even by 2016.
"We can unfortunately make no commitment.
We are going to spend that money and principally there's a number of tranches that we're spending it on," he said.
"We are spending it on development of the metallurgy.
We're spending it on some pre-mining activities of the open cut mine." At the time it mothballed the expansion plan, BHP said it was keen to investigate a cheaper extraction method, known as heap leaching.
The SA Government had said hundreds of millions of dollars could be spent in the state on researching new technology for the mine.
The Greens had been keen to see the indenture lapse, urging a new deal be negotiated which could be more attractive for South Australians.
Greens leader Mark Parnell questioned why BHP Billiton should be given "four more years for a dud project?" "It will be just as bad a deal in 2016 as it is now," he tweeted, and urged that Parliament disallow the extension.
The Opposition will support the extension, pending a briefing on the matter later in the week.