Zimbabwe's main opposition leader says there has been no progress in power-sharing talks with the ruling ZANU-PF party.

In a statement Wednesday, Morgan Tsvangirai called for former South African President Thabo Mbeki to step down as the talks' chief mediator.

He said Mbeki does not understand the problems in Zimbabwe, and accused him of having "partisan support" for ZANU-PF.

Negotiators for ZANU-PF and the opposition Movement for Democratic Change met in Johannesburg today and Tuesday in an effort to advance a September power-sharing deal.

The parties have been divided over how to allocate key cabinet posts. 

Pressure is growing on the parties to end their disputes and focus on fixing Zimbabwe's humanitarian crisis.  The United Nations says more than 360 people have died in a cholera outbreak, amid a breakdown in health services and a chronic food shortage.

Earlier, Botswana's foreign minister said the international community must isolate Zimbabwe to end the regime of President Robert Mugabe.

In an interview aired on British radio Wednesday, Phandu Skelemani also said African countries need to close their borders with Zimbabwe.  Skelemani said President Mugabe could not stay in power if his landlocked country was cut off from fuel for a week. 

Some information for this report was provided by AFP and Reuters.