Jun 18 - South Africa's ruling ANC party leader Jacob Zuma said he didn't think a free and fair vote was likely in Zimbabwe's run-off presidential poll next week. Zimbabweans will vote in a second round presidential poll later this month, after opposition Movement for Democratic Change (MDC) leader Morgan Tsvangirai beat President Robert Mugabe but was adjudged to have failed to get an outright majority in the March 29 election. South African President Thabo Mbeki is in Zimbabwe for talks with Mugabe. Mbeki has led regional mediation efforts in the increasingly violent crisis and has drawn criticism for his diplomatic approach towards the Zimbabwean leader. Earlier this week, Britain and the U.S. urged the Zimbabwean leader to allow a broader international observer mission. Monitors from countries critical of Mugabe have been banned from observing the election. Helen Long reports.