A union representing about half the workers at power utility Eskom called off a strike over pay due to start on Wednesday at the state-owned firm after a court declared the planned industrial action illegal.
The South African Transport and Allied Workers Union (Satawu), which represents strikers in a pay dispute at the state-owned logistics group Transnet, said it had issued notices for sympathy actions at other transport and shipping firms.
These will start next Tuesday if the dispute with Transnet, where a strike is now in its third week, is not resolved, it said.
The Transnet strike is already affecting ports and railways, and has held up exports of metals, cars, fruit and wine to Europe and Asia, as well as imports of vehicle parts and fuel supplies in Africa's biggest economy.
Satawu, with 39 percent of Transnet's 54,000 workers, wants its members, including employees of South African Airways, to join sympathy strikes to force Transnet to increase its pay offer.
It also asked workers at the country's coal export terminal to join the action, which is legal under South African laws.
"After further consultation with members it is the intention also to issue secondary strike notices on the Road Freight Association, whose members are road hauliers, as well as on aviation companies including SAA (South African Airways)," Satawu said in a statement issued late on Monday.
The World Cup starts on June 11th, and the world governing body FIFA said imports of some equipment for the tournament had been affected.
Transnet said on Tuesday that with 65 percent of its workers back at work it managed to move all crucial shipments, including World Cup cargo and jet fuel.
Fuel imports through South Africa to landlocked Botswana have been halved by the strike, and Botswana's energy minister was in Mozambique to try to secure long-term alternative supply routes through Maputo, government officials said.
Four Metrorail commuter train coaches were set alight on Tuesday, but no injuries were reported. It was not immediately clear who was behind the attacks. Metrorail faces a parallel national strike by Satawu over a pay dispute.
Business Unity South Africa (BUSA) said each two-week period of the strike could cost the economy about 7 billion rand (£620 million) or 0.2 percent of gross domestic product.
"Supply chains are being severely disrupted and in many cases export contracts have been permanently lost. Retrenchments may now also be looming," the industry body said in a statement.
Civil servants, including police and teachers, rejected a pay offer and may consider striking. Residents in an informal settlement protested on Monday, demanding better services.
Members of the bigger union at Transnet, the United Transport and Allied Trade Union, resumed work on Monday after accepting a pay rise of 11 percent, but the logistics group said the backlog could take a month to clear.
Agriculture, Fisheries and Forestry Minister Tina Joemat-Pettersson said the fruit industry alone
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