South Africa's NUMSA engineering and metalworkers union rejected a 10 percent pay offer from employers on Sunday and called on its 220,000 striking members in the sector to intensify nearly two weeks of industrial action.
"We are making a very clear statement that the strike continues and we call on our members to intensify the strike," South Africa's largest union said in a statement.
Employers have offered a 10 percent increase this year, 9.5 percent in 2015 and 9.0 percent the year after that, but NUMSA Secretary General Irvin Jim dismissed the offer and threatened to drag in 100,000 NUMSA members in other sectors not on strike.
"Should the employers continue with their reckless shenanigans and unreasonable demands, we might be left with no option but to call for targeted solidarity in all our sectors. This is seriously under consideration," he told a news conference.
The strike, which began only a week after the end of a five-month stoppage in the platinum sector, has hit companies supplying components to the automobile sector, with General Motors closing its assembly plant in the southern city of Port Elizabeth.
It has also damaged wider investor sentiment in Africa's most advanced economy, which is teetering on the brink of recession after a first-quarter contraction caused by the platinum strike.