Reports say the ANC deputy president has brokered a deal that will keep Cosatu's general secretary and largest affiliate in the federation.
Cosatu would not confirm on Tuesday that reinstated general secretary Zwelinzima Vavi would stay on under a deal brokered by ANC deputy president Cyril Ramaphosa.
"We will be releasing a statement tomorrow [Wednesday]," Congress of South African Trade Unions spokesperson Patrick Craven told the South African Press Agency.
The trade union federation's central executive committee held its first meeting since the suspension of Vavi was set aside by the high court in Johannesburg on Friday.
The SABC reported that Ramaphosa secured an agreement which would see Numsa remaining in Cosatu and Vavi continuing his duties.
Vavi, who was suspended from the trade union eight months ago for having an affair with a junior employee, returned to work on Monday. The National Union of Metalworkers of South Africa (Numsa) opposed Vavi's suspension and has been at loggerheads with Cosatu over the issue.
Numsa spokesperson Castro Ngobese could not be immediately reached for comment.
Ahead of his first day back at the office on Monday morning, Vavi called for unity within the trade union federation.
In an interview on SAfm, he said he heard in statements at the weekend by leaders of the National Union of Mineworkers and the National Education, Health and Allied Workers' Union that he would be suspended again this week.
"All I want to say ... this suspension and the status quo decided by the [Cosatu] congress, gives any union, including every leader, an opportunity to start afresh, to prioritise the interests of their members, to ensure Cosatu can be united again ... to address unemployment ... and inequalities," said Vavi.
"If congress wants to throw away all those issues ... it is a choice that comrades would have to make."
Vavi told the radio station it was time to move on and focus on union-related matters.
"I apologised a million times to every member of the federation," he said. "I committed an error, I accepted responsibility."
Affiliates supporting Vavi
The high court in Johannesburg set aside his suspension from Cosatu on Friday.
He was put on special leave in August last year, pending the outcome of a disciplinary hearing relating to his affair with a junior employee.
Following Vavi's suspension, Numsa lodged an application in the high court in Johannesburg challenging the decision. Cosatu in February then asked union to write a letter giving reasons why it should not be suspended or expelled from the federation.
Cosatu has been split between affiliates supporting Vavi and those supporting his suspension. But it emerged at a Numsa shopstewards' council at the Coastlands Hotel in Durban on Sunday that Vavi could face a renewed suspension.
"On Tuesday they will say let us continue with the disciplinary charges against Zwelinzima Vavi," Numsa deputy president Karl Cloete said at the council.
Cloete said that the current office bearers of Cosatu should be held accountable for wasting workers' money on hiring expensive lawyers to fight Vavi's reinstatement. – Sapa, additional reporting by Staff Reporter