"[Zuma] is very prepared to engage as far as he can in order to resolve the problems and the challenges that are faced by the Zimbabwean people, because every negative thing that happens in Zimbabwe has a direct impact on South Africa," Lindiwe Zulu said.

"He would like to speed up the process as quickly as possible," she said, adding that Zuma would soon travel to Zimbabwe to hold talks with members of the government in Harare.

Changes sought

The US government is looking for Zimbabwe to pick up the pace of political reform so that donor countries have sufficient incentive to release aid to Harare.

Washington has maintained sanctions against Robert Mugabe, the Zimbabwean president and his closest aides.

The US government has said that the lifting of sanctions is contingent on reforms being implemented by Mugabe's Zanu-PF party and the government it shares with Morgan Tsvangirai, a former opposition leader who is now the country's prime minister.

But Mugabe, who has been president of Zimbabwe since 1980, has said that Western sanctions and interference have caused the economic crisis in his country.

Clinton’s appeal on Friday comes amid efforts by the US government to build better relations with South Africa, which came under strain when the Bush administration was in power. 

"I know that the [South African foreign] minister and I are interested in making sure that our two countries not only lead but demonstrate the kind of co-operation that results in positive results for the people of the world," she said.

Clinton later went to HIV/Aids treatment centre in Cullinan, east of Pretoria, where she held talks with Pakishe Aaron, South Africa’s health minister.

"We have to make up for some lost time, but we are looking forward," Clinton said, in reference to what Washington called delays by the former South African government in addressing the health crisis.