There are no signs of an end to the dispute between Satawu and the Passenger Rail Association of South Africa, the union said on Wednesday.
Metrorail trains will be running in Gauteng from Monday following a strike that left thousands of commuters stranded nationwide last week.
Train commuters will have to wait until Monday for Metrorail trains as one of the transport unions had not signed a deal with Parsa by Thursday night.
Unions have reached a proposed wage deal with Transnet, which if accepted by members will end a strike that paralysed rail and port traffic.
The South African Trade and Allied Workers Union strike against Transnet will go ahead on Monday, but will not affect Gauteng Metrorail services.
Unions are calling it the biggest rail strike in South Africa — will affect the movement and delivery of everything from car parts to petroleum.