Tsvangirai, the leader of the Movement for Democratic Change (MDC), told supporters in Domboshava that fraud was the only thing that would keep him from victory.
"This time we won't fail," he said.
"It's now time to give Mugabe a red card and his pension. Those who refuse to join this bandwagon will need cleansing."
The military patrolled the capital Harare in armoured personnel carriers and security forces across the country were placed on full alert as Zimbabweans prepared for Saturday's poll.
Al Jazeera's Kamahl Santamaria, reporting from Harare, said that the situation in the capital was tense considering how people had reacted after a disputed election in Kenya.
Zimbabwean security chiefs said on Friday that they are ready to confront any violence that may surround the elections.
Augustine Chihuri, police commissioner, said anyone who harboured "evil" intentions would face the full force of the law.
"Those who have been breathing fire about the Kenyan-style violence should be warned that violence is a poor substitute for intelligence and that it is a monster that can devour its creator, as it is blind and not selective in nature," he said.
Mugabe himself warned his opponents to not even "dare" think about resorting to violence in the event of his victory.
Tsvangirai told Al Jazeera that there should be no violence on behalf of his party but could not give any assurances as to how the people of Zimbabwe would react.Rigging allegations
Moeletsi Mbeki, a political analyst, said that he did not expect violence but said that Mugabe could rig the elections in his favour.
"He will do exactly what Mwai Kibaki, the Kenyan president did, which is to write himself a winning number of votes irrespective of what the votes say."
In their first joint statement, Morgan Tsvangirai and Arthur Mutambara, leader of a breakaway MDC faction, along with Simba Makoni, Zimbabawe's former finance minister, said on Thursday that an independent scrutiny of voters' lists showed severe discrepancies.
Makoni, who is standing as an independent candidate, who spoke for all three groups opposing Mugabe, said: "There is a very well thought out and sophisticated plan to steal the election from us."
Tsvangirai urged voters to remain at polling stations after casting their ballots, in order to protect their votes.
He also called on public servants not to defraud voters.
"Mugabe cannot rig elections by himself. If someone tells you to falsify the results of the elections, ignore the instructions, because it is unlawful," he said.
The opposition said the voter registration list shows that between December 2007 and February 2008 the number of new voters increased by up to 11 per cent in sparsely populated rural areas, where the ruling Zanu-PF party holds most power.
This compares with a 2 per cent increase in urban opposition strongholds, the oppostion says.
"This is a five-fold difference which is not supported by our urban and rural demographic profile. We don't understand the discrepancy," Makoni said.
According to the Zimbabwe's electoral commission, 5.9 million people were eligible to vote in Saturday's combined presidential, parliamentary and local council elections.
However, the MDC revealed documents, leaked from the state security printer, showing nine million ballot papers ordered by the election commission.
Tsvangirai and the MDC allege that surplus ballot papers will be used to rig the vote.
State media on Friday predicted that Mugabe would win an outright majority in the first round of voting, thus negating the need for a run-off within three weeks.