SINGAPORE, Feb. 23 -- Global copper stockpiles probably will fall in the "longer term" as mining companies struggle to increase supplies, said Anglo American Plc's head of copper.

"There aren't enough high-quality projects in the world," Anglo's John Mackenzie told reporters today in Santiago, Chile. "It won't be easy to maintain a balance."

Demand for the metal used in plumbing and wiring may rise 6 percent this year while short-term prices are set to fluctuate, he said. London-based Anglo is selling assets to focus on copper and iron-ore mines in South America.

Anglo plans to spend more than $1 billion to develop mines in Chile this year after last year's $926 million investment, Mackenzie said. The company plans to double copper output by 2017, he said.

An expansion at its Los Bronces copper mine in Chile, which will cost $2.3 billion to $2.5 billion, will be completed in the fourth quarter of next year, Miguel Duran, Anglo's manager for Chile, said at the same event. The expanded mine will produce 490,000 metric tons a year for the first three years, he said.

Anglo and partner Xstrata Plc will decide next year whether to expand their Collahuasi copper mine in Chile, Duran said, adding the partners may build a seawater processing plant to double output. Anglo and Xstrata Plc each own 44 percent of the Collahuasi copper mine in northern Chile.