Zuma beat President Thabo Mbeki last month to take the top post in the ruling African National Congress in a leadership battle that exposed deep divisions in the party.

ANC deputy president Kgalema Motlanthe is respected by both the Mbeki and Zuma camps in the ANC and has been touted as a compromise candidate if Zuma's legal problems force him out of the race for the presidency ahead of a 2009 general election.

"We have lots of work to do in preparation for the incoming elections ... So, no useful purpose will be served by any such change (to cabinet)," Motlanthe, told Reuters.

He denied newspaper reports that the ANC's powerful National Executive Committee (NEC) was pushing for him to be part of Mbeki's cabinet.

"It hasn't happened because it doesn't exist. It is total fiction," Motlanthe said after top NEC officials briefed the ruling party's parliamentary caucus.

Given the ANC's electoral dominance, the ANC leader is virtually assured of becoming state president. Mbeki is constitutionally barred from a third term.

But, Zuma's legal woes could scupper his political ambitions. He goes on trial for money-laundering, racketeering, fraud and corruption charges in August and has said he would stand down as ANC leader if convicted.

The party's general secretary Gwede Mantashe said the NEC was not considering pushing Motlanthe into a cabinet post.

"We are not preoccupied with the deployment of Mr. Motlanthe. We are preoccupied with the smooth workings between the party structures and those deployed in government," Mantashe told a media briefing.

Political analysts have said friction between the Mbeki-controlled government and the Zuma-led ANC could harm South Africa's economic prospects and its programme to uplift millions of blacks still mired in poverty.