South Africa's ruling African National Congress (ANC) nominated just two candidates to run for its top job on Saturday, leaving President Cyril Ramaphosa facing the health minister he suspended over corruption allegations in a party vote.

The winner will have the ANC's blessing to run for president in elections in 2024 under its banner.

The ANC's five-day conference in Johannesburg has exacerbated a divide between its two main rival power blocs, one coalescing around the incumbent Ramaphosa and the other around former President Jacob Zuma.

Former health minister Zweli Mkhize, who emerged as the sole challenger to Ramaphosa, is allied to Zuma's faction. Ramaphosa put Mkhize on special leave last year in the wake of allegations that his department irregularly awarded COVID-19-related contracts to a company controlled by his former associates.

Mkhize, who also ran against Ramaphosa when the latter won the position in 2017, denies wrongdoing. Both had been nominated ahead of the conference, and no additional candidates were added from the floor as nominations were concluded around midnight on Saturday.

Delegates at the ANC's conference must decide which candidate is best placed to revive its fortunes on December 23.

The ANC is less popular than ever and faces the very real prospect of losing its majority in parliament.

Ramaphosa's opponents want him to step down over a scandal involving the discovery of a stash of cash at his farm. He has denied wrongdoing and has not been charged with any crimes.

Ramaphosa's political woes have galvanized supporters of former leader Zuma, who is himself being investigated for allegedly colluding with three Indian businessmen to siphon off state funds during his tenure between 2009 and 2018, charges he denies.

Investors fear a return of Zuma's power bloc could threaten reforms Ramaphosa has made to try to clean up grand corruption associated with his predecessor, already under strain because of the farm money scandal.

Mkhize was always the strongest challenger from Zuma's camp – the other main ones, Nkosazana Dlamini-Zuma, a cabinet minister and Zuma's former wife, and Tourism Minister Lindiwe Sisulu – did not qualify to be on the ballot.

(With input from Reuters)