SYDNEY — Global miner BHP Billiton Wednesday delayed multibillion dollar expansion plans for its massive Olympic Dam project to improve the economics of what is set to be the world’s largest open pit mine. The announcement comes as the world’s largest miner reported a near 35-percent slump in full-year net profit. Chief executive Marius Kloppers said current market conditions, including subdued commodity prices and higher capital costs, had contributed to the decision to recast plans for the development reportedly worth US$20 billion. “As we finalized all the details of the project … it became clear the right decision … was to continue studies to develop a less capital intensive option to replace the underground mine at Olympic Dam,” Kloppers said. BHP Billiton has proposed creating a massive open mine pit, which will operate alongside its existing underground mine, to deliver more copper and uranium to meet global demand. Kloppers said the long-term copper market remained strong and it would continue to investigate other designs for the huge project. “We want to find the right solution to unlock this resource,” he said. The miner had a deadline of Dec. 15 to approve the expansion, in line with an agreement reached last year with the South Australian state government, but said it would now not meet that date. It said it would discuss its decision with the South Australian government which had hoped the project would create more than 13,000 jobs and contribute AU$45 billion (US$46.9 billion) to the economy over three decades. BHP said its decision would cost it US$242 million after tax in impairment and other charges in the 2012 financial year. BHP’s existing underground mine at Olympic Dam is already Australia’s largest and national Resources Minister Martin Ferguson has said the site had the potential to become one of the world’s largest mines, if not the largest.