The South African government on Tuesday warned the Western powers to pull back on their efforts to heap additional sanctions on the Zimbabwean government, saying such initiatives could jeopardize efforts to peacefully resolve the country's post-election crisis, adding that expanding the mediation process would not help achieve the desired outcome.

Zimbabwe's ruling Zimbabwe African National Union-Patriotic Front and opposition Movement for Democratic Change last week opened preliminary talks to set the ground rules for more substantive discussions on power sharing to resolve a post-election crisis.

The MDC won a majority in parliament in March elections which however ushered in months of political violence mainly aimed at opposition members, leading to a widely condemned June 27 presidential run-off won by President Robert Mugabe, the only participating candidate. His opponent, the MDC's Morgan Tsvangirai, pulled out June 22 over mounting violence.

Johannesburg correspondent Benedict Nhlapho of VOA's Studio 7 for Zimbabwe reported that Deputy Foreign Minister Aziz Pahad told reporters that Zimbabwe's opposition has yet to formally request expansion of mediation to include an African Union envoy.

Responding, spokesman Nelson Chamisa of the Movement for Democratic Change formation of former presidential candidate Morgan Tsvangirai insisted in an interview with reporter Blessing Zulu that  the mediation must be expanded if it is to succeed.

Independent political analyst Chris Maroleng said that if Mbeki insists on mediating alone this could negatively affect the outcome of the talks.

Meanwhile, members of the Southern African Development Community’s troika on politics and security were set to meet Friday and Saturday in Durban, South Africa, to examine the crisis and assess ongoing diplomatic efforts to come up with a power-sharing solution.

SADC and the AU are under heavier pressure to resolve the crisis in the wake of the defeat last week in the United Nations Security Council of a U.S. resolution to impose more sanctions on Harare. China and Russia vetoed the measure, saying international security was not at risk and that the African diplomatic process should be given chance to produce results.

General Secretary Zwelinzima Vavi of the Congress of South African Trade Unions repeated Tuesday that Mr. Mbeki's mediation since March 2007 has been a failure.

U.S. Secretary of State Condoleezza Rice told a Washington conference on African trade that African nations must do more to hold Mr. Mugabe accountable for his actions.

U.S. Assistant Secretary of State for Africa Jendayi Frazer told a U.S. Senate hearing on the Zimbabwe crisis that the SADC session coming up later this week in Durban will be critical to expanding the mediation process to achieve agreement on power-sharing.

More reports from VOA's Studio 7 for Zimbabwe...