Former South African Deputy President Jacob Zuma has been charged with rape which he has vehemently denied.
Zuma is under increasing pressure
Mr Zuma was sacked as deputy president in June, and charged with corruption, which he also denies.
In the last month, public support for Mr Zuma has waned amid reports that police were investigating rape charges.
Mr Zuma is still deputy leader of the governing ANC party, but says he will suspend his participation in party structures during the trial.
Mr Zuma appeared briefly in court early on Tuesday and was released on bail of 20,000 rand ($3,000).
"I wish to state clearly that I am innocent of these charges," Mr Zuma said in a statement issued after the court appearance.
"Given the nature and the seriousness of these allegations, I have voluntarily decided to suspend my participation in the leading structures of my organisation for the duration of this trial," the statement added.
"These structures are the National Executive Committee, the National Working Committee, the officials' meetings and the National Deployment Committee.
"I will however carry on with the general activities of the ANC as expected of all members of our organisation. This decision does not affect my position as ANC Deputy President."
Mr Zuma is to appear in the magistrate's court again on 13 February, and it is likely that the case will then be transferred to the High Court.
The ANC National Working Committee is to discuss the charges on Tuesday evening and is expected to issue a "comprehensive statement" on Wednesday.
Mr Zuma was previously seen as the natural successor to President Thabo Mbeki.
While Mr Zuma's many supporters within the ANC and its allies stood by him as he was charged with corruption, his support has ebbed since the rape allegations first emerged in the press last month.
A woman in her 30s reportedly told the police she was raped at Mr Zuma's house in Johannesburg.
Mr Zuma is reported to have told friends and supporters that he did have sex with the woman, but that it was consensual.
The incidence of sexual violence in South Africa is among the highest in the world, and at the political level is regarded very seriously.
The South African Communist Party and the Congress of South African Trade Unions (Cosatu) - both ANC allies whose supporters cheered Mr Zuma at his court appearances on corruption charges - said recently they did not support him as successor to Mr Mbeki.
The corruption case has caused the party its biggest internal crisis since it was elected to power in 1994.
The corruption charges stem from the trial of Mr Zuma's former financial adviser, Schabir Shaik, who is appealing against a 15-year jail sentence for fraud and corruption.