Twenty-eight female guards were unfairly dismissed by a security company because the client‚ Metrora.
THE National Union of Mineworkers threatens it will halt 2010 World Cup projects unless construction companies give workers a 15percent salary increase.
"Construction companies have made huge profits and we know they have the money," the union's spokesperson Lesiba Seshoka said yesterday.
More than 50000 of the union's members might down tools this week over pay.
Construction companies have increased their offer to 8,5percent from 7,5percent.
The union held back-to-back meetings last week with the employers' body, the South African Federation of Civil Engineering Contractors, at the CCMA offices.
Seshoka said Safcec would present its offer on Thursday.
"If that offer is not 15percent then we will strike," he warned.
Deadlines for big projects such as the 2010 stadiums and Gautrain would be under threat, he said.
The companies include Grinaker LTA-Interbeton JV, Murray and Roberts and Group 5.
The companies do not have contingency plans to bring in other workers in case of a strike, said Group 5's human resources executive Junaid Allie.
Allie said Group 5 has "only made single-digit profit" and not "huge amounts of money" as the union claimed.
He said his company was doing everything it could to avert the strike.