The head of the Zimbabwe African National Union -- Patriotic Front issued the ultimatum to the opposition group this week as ongoing talks for a unity government have resulted in little progress, SW Radio reported Thursday.

"If after tomorrow (Thursday), Tsvangirai does not want to sign, we will certainly put together a Cabinet. We feel frozen at the moment," Mugabe said.

MDC spokesman Nelson Chamisa responded to the president's ultimatum by labeling it a veritable "death sentence" to unity negotiations.

"Dialogue is not done with threats, arm-twisting and bully tactics. We shall not swallow the ZANU poison," Chamisa said. "Mugabe is effectively issuing a death certificate to the talks."

South African President Thabo Mbeki is set to arrive in Zimbabwe next week to help with the ongoing negotiations.

The Herald (Zimbabwe) said Mbeki is to meet with MDC head Morgan Tsvangirai in hopes of pushing the party to accept Mugabe's current power-sharing deal.