The ANC electoral commission was expected to announce on Thursday whether deputy president Kgalema Motlanthe would run against President Jacob Zuma at the party's national conference in Mangaung.
The commission was scheduled to hold a news briefing in Johannesburg at Luthuli House.
On Wednesday three radio stations reported Motlanthe had accepted the nomination.
SAfm “reliably learnt” that Motlanthe would accept nomination for the top position in the African National Congress. Eyewitness News and Jacaranda News carried similar reports.
ANC treasurer Mathews Phosa confirmed to Sapa he had accepted the nomination to stand for the deputy presidency.
“I've accepted the nomination by the ANC branches for me to stand as deputy president,” said Phosa.
“I am abiding by what they (the ANC branches) put forward to me.”
Motlanthe's spokesman Thabo Masebe declined to confirm the reports on the deputy president's acceptance.
“The matter is now in the hands of the ANC's electoral commission. I know they have been in contact with the deputy president, but the deputy president won't make any statements about that because he respects the fact the electoral commission is responsible for the process of nominations.”
Masebe said the ANC's electoral commission would announce who was nominated.
Jacaranda FM on its Twitter page said Sports Minister Fikile Mbalula had also accepted nomination for the position of secretary general.
His spokesman Justin de Allende said: “He is a member of the ANC. As a member of the ANC he's eligible and duty-bound to accept any form of deployment, as members of the ANC, request of us...” - Sapa