MELBOURNE, Australia (AP) -- BHP Billiton, the world's biggest miner, Tuesday reported a better-than-expected half-year profit of $8.1 billion as cost cuts offset lower commodity prices.

The Anglo-Australian company's shareholders could participate in a company share buyback in six months. Chief executive Andrew Mackenzie said net debt could be down to $25 billion by then, a level he has previously said could trigger a capital return.

BHP's net profit for the July-December half year jumped 83% to $8.1 billion from $4.4 billion a year earlier.

Stripping out one-time gains and losses, profit was up 31% to $7.8 billion. That was well ahead of analyst forecasts of about $7 billion.

Mackenzie was positive about the prospects for the global economy this year and the impact on demand for iron ore and other commodities.

"The balance of risk to global growth is skewed to the upside, particularly given the broad-based alignment of macro-economic indicators in the major developed economies," he said.

BHP had removed $4.9 billion in costs and that was expected to increase to $5.5 billion by the end of the fiscal year, he Mackenzie said.

"The commitment we made 18 months ago to deliver more tons and more barrels from our existing infrastructure at a lower unit cost is delivering tangible results," he said.