Codelco, the world's largest copper miner, said on Friday it produced roughly 1.18 million tonnes of the red metal in the January to September period, a 0.3 percent decrease year-on-year due to lower ore grades, harder rock and trickier production in deeper deposits.

The Chilean state miner's profits before tax and extraordinary items dived 61 percent to $2.672 billion due to an unusually high comparison base with last year, when Codelco bought a stake in Anglo American's Sur properties in Chile, as well as lower copper prices and higher sales costs.

Codelco expects its full-year output to be in a similar range to last year's, when production fell to its lowest level since 2008, Chief Financial Officer Ivan Arriagada said in presenting the firm's results.

Output at Codelco's Chuquicamata, Radomiro Tomic, Salvador and Andina mines fell, though increases at the El Teniente and Gabriel Mistral deposits helped curb the overall drop, Codelco said.

The massive, century-old Chuquicamata mine is emblematic of Chile's tired deposits. The mine produced 237,000 tonnes of copper in the January to September period of this year, a roughly 5 percent fall compared with the same period of 2012.

Codelco must urgently revamp its aging deposits, or sinking ore grades will slash output in the next few years.

But the company has struggled to finance its ambitious, multi-year investment plan, estimated at about $27 billion, after the government awarded the company less money than it had hoped for this year. Codelco hands all its funds over to the state, which then decides how much to transfer back for investments.

Former President and front-runner Michelle Bachelet, who is poised to be elected to top office in December's run-off vote, says her government would continue to fund the miner. However, it does not mention how.

Factoring in Codelco's stake in El Abra and Anglo Sur, production rose 4.5 percent to around 1.31 million tonnes in the January to September period.

For a factbox on production, please see:

In addition to dwindling ore grades and weaker copper prices , Codelco is also struggling to contain costs. The company's direct cash costs were $1.652 per pound of copper in the January to September period, a 5 percent increase from 2012 levels.