Sactwu is currently conducting a strike ballot following a deadlock in wage negotiations.
General secretary Andre Kriel said Wednesday’s "leadership" talks were open and frank.
"[However] the parties could regrettably not reach a settlement. The trade union has committed itself to further talks during the course of next week."
The union was proceeding with the strike ballot.
By close of business on Tuesday the union had balloted just over 6000 members in 41 companies. The union expects that close to 15,000 members would have been balloted by the end of Wednesday.
Employers are offering a five percent wage increase; the union wants 7.9.