UPDATE 1-Court allows SAfrican construction workers to strike

* Strike to affect power stations, highways, airports

* Strike to delay completion of 2010 soccer stadiums

(Adds details, employers comment)

By Tiisetso Motsoeneng

JOHANNESBURG, July 6 (Reuters) - About 70,000 South African construction workers are expected to strike on Wednesday, halting work across the country including on stadiums for the 2010 FIFA World Cup, after a court refused to ban the action.

The National Union of Mineworkers said in statement on Monday that it had won the case against the South African Federation of Civil Engineering Contractors (SAFCEC), which had last week asked the court to prevent the union from striking.

"Employers must expect no mercy from us, they must deliver 13 percent or we will strike until 2011," said Bhekani Ngcobo, the NUM's Negotiator at SAFCEC in a statement.

World Cup organisers said last week they would meet trade union officials to try to ensure a strike does not delay completion of stadiums beyond target but would not interfere in workers' democratic rights to strike.

Officials have said previously that the 10 stadiums for the World Cup, half of them new, will be delivered on target by December, although there have been some reports that the Green Point venue in Cape Town may be delayed into next year.

After the collapse of prolonged negotiations with the employers organisation, NUM called the strike to support its demand for a 13 percent wage increase. Employers have refused to go beyond 10 percent.

"The interdict wasn't granted," said Joe Campanella, spokesman for SAFCEC, adding the unions and employers were in fresh talks to find a resolution but declined to say if the employer organisation would revise its offer.

Companies likely to be hit by the strike include Africa's top construction firm Murray & Roberts Holdings Ltd (MURJ.J), WBHO (WBOJ.J) and Group Five (GRFJ.J).

South Africa's state-owned utility Eskom's [ESCJ.UL] 4,800 megawatt Medupi power station could also be affected, slowing efforts to fill a chronic power shortage in the country.

Expansion work on the coal export facility, Richards Bay Coal Terminal could be delayed further, the union said. (Editing by Jon Boyle)