"We are talking to our members in the ports and rail sectors to join in a secondary strike. Import and export at ports will be shut down," SA Transport and Allied Workers' Union secretary general Zenzo Mahlangu said.

Talks between the unions and the Road Freight Employers' Association (RFEA) collapsed on Thursday evening.

The two week-long strike had been marred by violence and intimidation. Drivers wanted a 12 percent salary increase while employers offered 8.5 percent for next year, and another 0.5 percent the following year.

The RFEA accused the union of "shifting the goal post".

"[The deal] met their demand of 18 percent in the first two years, plus an additional third year included in the cycle, resulting in a three-year agreement," RFEA spokeswoman Magretia Brown-Engelbrecht said in a statement.

Mahlangu said the employers were not taking the workers seriously.

"We told them workers do not want to be locked in a three-year agreement. We compromised and proposed a two-year agreement."

A three-year deal would not allow workers to negotiate further should inflation increase, said Mahlangu.

No further meetings were planned between the unions and the association.

The RFEA would on Friday argue for an interdict in the Labour Court to stop the strike. Mahlangu said his union was ready to oppose the application.