Harare - Talks between Zimbabwe's parties on a power-sharing government were due to resume Monday as South African President Thabo Mbeki flew to Harare to broker fresh negotiations between President Robert Mugabe's Zanu-PF and Morgan Tsvangirai's Movement for Democratic Change (MDC).

Mbeki's office confirmed to South African media that he was on his way to Zimbabwe to try to breathe new life into the talks that have foundered over how Mugabe and Tsvangirai would share power in a unity government.

The MDC said at the weekend the issue was a matter for a new interim constitution.

"The issue is about the constitution which gives too much power to the president," MDC Secretary-General Tendai Biti told a rally in Gweru, 300 kilometres southwest of Harare, on the 9th anniversary of the MDC's founding.

"We need an interim constitution that deals with that," he said.

Mugabe has threatened to forge ahead with forming a government without the MDC, unless Tsvangirai signs up to a deal that would see Tsvangirai become prime minister but without the full powers of a head of government.

Tsvangirai on Sunday reiterated his belief that no deal was better than a "bad deal." His party has the most seats in the lower house of parliament, making it difficult for Mugabe to govern without him.

Tsvangirai also gained more votes than incumbent Robert Mugabe in March elections but failed to pass the 50 per cent threshold to unseat the controversial president.

The MDC, the West and a handful of African countries rejected Mugabe's victory in a run-off ballot at the end of June in which he was the only candidate.

The African Union at a summit in late June called upon Mugabe to share power with the MDC. (dpa)