Eskom, which produces about 95 percent of South Africa's electricity, has rationed power through a process known as load-shedding since January in response to a supply crisis that has scared investors and clouded the economic outlook.

Mines, one of the cornerstones of South Africa's economy, have had their electricity supply reduced, and millions of homes and businesses are regularly plunged into darkness.

"The system is still tight and vulnerable," Eskom spokesman Andrew Etzinger said in a presentation outlining strategies before the start of winter, when electricity use tends to peak.

"I would fully expect that there will be days when our system will not be able to meet demand. There will be days of load-shedding," Etzinger said. Eskom expected disruptions to its system to be "minor" during the period.

He noted the utility was moving ahead with construction of coal-fired power stations as part of a $45.6 billion infrastructure expansion programme. There are also plans to build nuclear power plants.

The African Development Bank (AfDB) announced on Wednesday it had lent $500 million to Eskom to help fund the expansion, which is regarded as critical to ensuring South Africa's economy continues to grow.

"The bank's loan is intended to assist the government in achieving the GDP growth target of 6 percent per annum from 2010," AfDB said in its 2007 annual report, which was released at a conference in the Mozambican capital Maputo.

PRICE HIKE FURY

As part of its efforts to fund the infrastructure programme, Eskom has requested a revised 53 percent increase in electricity tariffs for 2008/2009. It had received approval for a 14.2 percent increase for the year.

The ruling African National Congress and its leftist allies have opposed the request. Critics argue the poor and workers will be unable to afford electricity.

Etzinger said Eskom was open to discussing its price hike proposal at an energy summit later this week and there were other "scenarios" on the table. But he stressed the utility needed to be financially stable.

Eskom's senior management has played down hopes the utility could increase its electricity reserves quickly and say reducing consumption is the only quick fix for the crisis.

Eskom has blamed its problems on a combination of factors, including the failure of the government to invest in electricity generating plants, maintenance problems at its existing facilities and wet weather that affected coal supplies.

All the utility's power generating stations have at least 11 days of coal supplies, Etzinger said.

Nationwide power cuts in January forced large gold and platinum mines to shut down operations for five days, pushing precious metal prices higher. The mines are now operating at 90 to 95 percent of their normal electricity supply.

Some observers worried the soccer World Cup, which South Africa hosts in 2010, could be affected despite official reassurances stadiums will have generators for the tournament.