South Africa's National Union of Mineworkers members at Impala Platinum on Friday rejected a revised pay rise offer from the world's second largest producer of the precious metal and will refer the dispute to arbitration.

The platinum sector is the latest to be affected by a wave of disputes in the country's mid-year strike season after stoppages in the steel, fuel and mining sectors threaten to dent growth in Africa's biggest economy.

The members unanimously rejected the revised offer. We insist on a double-digit increase across the board, said Eddie Majadibodu, the NUM's chief negotiator at Implats.

Implats had raised its offer to between 8 and 10 percent, while the union has been asking for 14 percent, nearly triple the inflation rate. NUM workers in the gold and coal sectors have already reached deals for 7 to 10 percent increases, which could serve as benchmarks in the platinum talks.

The labour disputes are likely to unnerve investors already wary about putting money into the country due to steep power tariff hikes and a debate around nationalisation of the country's mines.

Talks at Amplats are set to continue on Friday. The two sides moved closer as the company raised its offer on Thursday to 7.5-8 percent, while the union lowered its demands to between 11 and 12.5 percent.

Implats and bigger rival Anglo American Platinum (Amplats) account for two-thirds of global platinum supply and any strike could push prices higher.

BURNING TRASH

In a separate dispute, more than 200,000 water, sanitation and refuse workers seeking 18 percent wage increases are expected to march in Johannesburg on Friday after setting fires and looting vendors at rallies in Cape Town this week.

The NUM, with more than a quarter million members in various sectors, has also threatened a strike at state utility Eskom, which supplies almost all of the country's power, after rejecting a 7 percent pay rise offer.

Any significant pay rises would affect the utility's strained balance sheet and could lead to further steep rises in electricity tariffs.

Further wage hikes will make it more costly to hire the workers needed to bring power by 2014 to the 25 percent of the country's households that still have no access to electricity.

Wage deals over the past years of double to triple the inflation rate have made the country less competitive by driving up the cost of a workforce which is already more expensive and less efficient that those in emerging market peers.

But the ruling African National Congress, which is in an alliance with organised labour, does not want to antagonise a group that has supplied it with millions of votes, by pushing workers to accept more modest pay increases.

African National Congress Eskom Precious metal South Africa