South Africa's electricity company Eskom said it would have to extend rotational power cuts to Thursday as its units continued to generate less power than was needed.

Eskom had initially indicated it would suspend the latest bout of load-shedding on Monday morning, but said in a statement late on Sunday that its system remained under stress.

"While good progress has been made in replenishing water for our pumped storage schemes, we have not fully replenished diesel for our open cycle gas turbines, necessitating that Stage 2 load-shedding be implemented during the week until Thursday," it said.

"While rotational load-shedding is unavoidable, in an effort to minimise the impact on traffic, we will endeavor to provide a break in load-shedding from 06:00 to 09:00 each day in the week, when possible."

Eskom, which supplies about 95 percent of the country's electricity, has been forced to effect load-shedding on and off for months to avoid tripping the national grid, partly due to the frequent breakdown of its infrastructure after years of inadequate maintenance.

It has generally applied "stage 2" load-shedding which involves suppressing up to 2 000 megawatts of demand, but was last year forced to accelerate this to an unprecedented "stage 6" -- involving up to 6 000 MW, as the grid came under immense pressure.

Last Friday the utility's new chief executive Andre de Ruyter warned that South Africa would experience increased load-shedding for the foreseeable future because of the problems inherent in the power system.

"Our system is constrained, it is unreliable and unpredictable and it is prone to unplanned outages and breakdowns," de Ruyter told a news conference.