Pretoria: Zimbabwe's opposition leader said on Saturday he would return home within two days to contest a run-off against President Robert Mugabe and deal him a "final knockout" after almost three decades in power.

But chances of a speedy end to the stalemate that has gripped the country since a disputed March 29 election appeared remote after Zimbabwe's justice minister rejected Movement for Democratic Change (MDC) leader Morgan Tsvangirai's pre-conditions for taking part in the run-off.

Tsvangirai said he would only participate if international observers and media get full access to ensure the run-off is fair. He said the country's electoral commission was discredited and should be revamped. Justice Minister Patrick Chinamasa shrugged off the demands.

"The runoff will be held within the framework of the constitution and the electoral laws. There will be no conditionalities that will be outside this framework," he said.

Zimbabwean political commentator Eldred Masunungure said Tsvangirai's demands made a short time-frame hard.

"Two weeks is a short time for observers to get in and make some effective presence," he said.