South Africa's Gold Fields will consider doubling the size of its $450 million Cerro Corona copper and gold project in Peru once the mine reaches full output in December, a newspaper said on Thursday.

Juan Luis Kruger, the head of Gold Fields' South American operations, told South Africa's Business Report the company's equivalent reserves in Peru, which include gold and copper-rich ore, could reach as much as 5.7 million ounces, up from 5 million ounces, due to higher metal prices.

Viability studies of the proposed expansion would be ready in about three years' time, Kruger told the newspaper during a tour of the mine. Expansion costs would be known then, he said.

Speaking in northern Peru, Kruger said to double the output from the open pit mine, located 90 km north of Cajarmaca in the Andes mountains, Gold Fields would have to double its reserves to 10 million ounces.

Kruger said Cerro Corona would contribute 8 percent to Gold Fields output and 20 percent to operating profit, once the mine hit full capacity of 140,000 ounces and 28,000 tonnes of copper.

Gold Fields, the world's fourth biggest gold miner, with eight operating mines in South Africa, Ghana and Australia, has said its ninth mine, Cerro Corona, is on track to begin production and the shipment of concentrate in the first quarter to end-September of 2009.

Gold Fields' yearly attributable production is about 4 million ounces. Like its peers in South Africa, the company has seen some mine output drop after state-owned power utility Eskom suffered a near collapse in the electricity grid in January, which led to a five-day countrywide mine shutdown.

Eskom has since supplied around 90 to 95 percent power to mines in the country, which the world's biggest source of platinum and major gold producer, trimming output further.