Former president Nelson Mandela called on workers to rise to the challenges of these troubling times, in a recorded message played for delegates at Cosatu's 10th national congress in Midrand on Monday.

"We urge you not to tire, not to despair when times are tough and to be resilient in these troubling times," Mandela said after saluting the Congress of SA Trade Unions (Cosatu) for its "tireless dedication" to millions of workers.

He urged the unions to continue to maintain the African National Congress as a united movement firmly rooted in the hearts and minds of millions of South Africans.

He said the conference took place at a "difficult time", with an economic recession threatening to derail the fruits of South Africa's young democracy.

"It is at times like this when we need men and women of wisdom to rise to the challenge," he said.

He called on Cosatu to continue to be the voice of the voiceless.