"I am so confident that in spite of the violence, come the second round they will reconfirm that rejection."
The election process has been marred by delays, violence and allegations of electoral fraud and the country's economic woes are growing deeper, with official inflation at 165,000 per cent and unemployment of 80 per cent.
Mugabe, 84, who has ruled the former British colony since independence in 1980, lost the first round by 43.2 per cent to 47.9 per cent against Tsvangirai and is now fighting for his survival.
Despite numerous reports from human rights and civil society groups in Zimbabwe stating the contrary, Mugabe accused the opposition Movement for Democratic Change (MDC) of fomenting post-election violence on Friday.
"The MDC and its supporters are playing a very dangerous game. They should know they cannot win that kind of war which they have carried to rural constituencies in the hope of destabilising our supporters," he told leaders of his Zanu-PF party.
Zimbabwean doctors, unions and teachers have reported a campaign of terror conducted by pro-government militias in rural areas against supporters and activists of the MDC since the March elections.
|Some Zimbabweans have had to leave home to|
seek refuge in neighbouring South Africa [AFP]
The MDC says at least 32 of its supporters have been killed in the unrest.
These reports have been bolstered by the UN, whose representative said the majority of violence had been directed at MDC supporters, and rights group Amnesty International.
Tsvangirai has made a series of demands to ensure a free and fair run-off election, including the presence of foreign peacekeepers and election monitors, but these have been brushed off by the authorities.
On Friday, an independent home-grown network of monitors that observed the first round said dozens of its activists had been assaulted by suspected Zanu-PF supporters since the March 29 election.
"We are already receiving a number of reports where our observers are saying it is no longer safe for them to observe the (run-off) election," chairman of the Zimbabwe Elections Support Network (ZESN), Noel Kututwa, said.
Tsvangirai, who was brutally attacked in police custody last March, also faces a threat of a treason charge after being accused of plotting with former colonial power Britain to bring about regime change.
Seen as a post-colonial success story in the first decade and a half after independence, Zimbabwe's economy has been in freefall since 2000 when Mugabe embarked on a land reform programme which saw thousands of white-owned farms expropriated.