While there was a significant site shutdown last year, sales are expected to increase in 2013 from mining high grades and a ramp-up in production at the Deep Ore Zone underground mine.

Concentrate production for the December quarter equated to 200 million recoverable pounds of copper and 221,000oz gold.

It was up 194% year-on-year for copper and 48% year-on-year for gold, which reflected the impacts of Grasberg's industrial relations disputes in the last quarter of 2011.

As part of the planned transition away from open pit mining in 2016, Freeport aims to produce about 240,000 tonnes of ore per day from several underground orebodies.

The Grasberg block cave development is due to start producing in 2017 while the Deep Mill Level Zone operation is expected to start in 2015.

"Over the next five years, estimated aggregate capital spending on these projects is currently expected to average $US715 million per year," Freeport said.