African National Congress (ANC) leader Cyril Ramaphosa pulled out of public events to focus on "pressing matters" on Friday, fuelling speculation that Ramaphosa was making a final push to force Jacob Zuma to step down as South Africa's head of state.

Zuma, in power since 2009 and battling corruption allegations, has been living on borrowed time since Ramaphosa replaced him as leader of the ruling party in December.

Ramaphosa and members of the ANC's 'Top Six' most powerful officials had been due to visit Archbishop Emeritus Desmond Tutu and supporters at various events in Cape Town. But an ANC spokesperson said they would not participate in those events due to "other pressing matters".

An ANC official in the Western Cape province said the schedule changes related to the party's push to force Zuma to stand down.

"We all know and anticipate that they are dealing with the current issue that is facing our country," Faiez Jacobs, the party's provincial secretary, told eNCA television.

Ramaphosa has been lobbying for Zuma to resign and has said he hopes to conclude talks with him over a transition of power "in coming days...in the interests of the country."

A spokesperson for Ramaphosa, who also serves as South Africa's deputy president, said the ANC leader no longer had any public engagements on Friday or Saturday. He said Ramaphosa had returned to Gauteng province, where the ANC's headquarters is located in the country's commercial capital Johannesburg.

Zuma's spokesperson did not respond to calls seeking comment.

The rand, which has tended to strengthen on signs that Zuma could step down before his second term as president ends next year, rose on Friday as investors increased bets that Ramaphosa would be able to unseat the embattled Zuma.

Ramaphosa is due to give a speech on Sunday as part of year-long celebrations to mark 100 years since the birth of liberation hero Nelson Mandela.

Zuma had been due to officiate at a diplomatic awards ceremony in Cape Town on Saturday, according to his office, but that event has been postponed.

Zuma has been South Africa's most controversial president since the end of white-minority rule in 1994, overseeing a tumultuous nine years marked by economic decline and numerous allegations of corruption.