The ANC Youth League will be joining Wednesday's nationwide strike, Congress of SA Trade Unions general secretary Zwelinzima Vavi said on Tuesday.
He said youth league leader Julius Malema was in solidarity with the action and would march with protesters.
Malema was still the league's representative as he was appealing his expulsion from the party, Vavi told reporters in Pretoria.
The strike is in protest against e-tolling and labour broking.
Vavi said Cosatu respected the ANC disciplinary committee's decision to expel Malema, adding that Malema's plans to take part in Wednesday's protest put Cosatu in a "tight corner".
However, everybody could participate in the march, including other political parties.
"We are calling on all workers, except those in essential services."
A total of 34 marches were expected to be held across the country on Wednesday.