Zimbabwe's Movement for Democratic Change (MDC) has publicly repudiated the mediation of South Africa's former president, Thabo Mbeki, in the country's crisis, while Botswana has suggested President Robert Mugabe could be forced from power by a blockade of his borders.

MDC leader Morgan Tsvangirai said in a statement issued Wednesday that the MDC's relationship with Mbeki - the Southern African Development Community (SADC) facilitator of talks on Zimbabwe - had irretrievably broken down.

Mbeki "does not appear to understand how desperate the problem in Zimbabwe is, and the solutions he proposes are too small," Tsvangirai said.

"In addition, his partisan support of [Mugabe's] Zanu-PF, to the detriment of genuine dialogue, has made it impossible for the MDC to continue negotiating under his facilitation," Tsvangirai added.

Tsvangirai has written to the chairman of the SADC, South African President Kgalema Motlanthe, asking that Mbeki "recuse himself."

Also on Wednesday, Botswana's foreign minister, Phandu Skelemani, attacked Mugabe's legitimacy in unequivocal language.

"Nobody recognizes that he's the head of any state," Skelemani told the BBC World News television programme, HARDTalk. "Remember, there is no government in Zimbabwe as we talk - de facto he is there but not in terms of the law."

Skelemani suggested that if the current talks on constitutional amendments designed to establish a legitimate government failed, the SADC should confess its mediation had failed.

In that event, the international community should "tell Mugabe to his face, that now you are on your own, we are switching off, we are closing the borders," Skelemani added. "I don't think he [Mugabe] would last. If no petrol went in for a week, he can't last."

However, Skelemani said, if SADC placed an embargo on Zimbabwe, it should be prepared to make food drops into the country until Mugabe stepped down, or its people would starve.