CEMENT GRIP
Analysts said Mugabe was pressing ahead with the election in a bid to cement his grip on power and strengthen his hand if he was forced to negotiate with Tsvangirai.
Mugabe has said he is willing to sit down with the MDC but would not bow to outside pressure, even from the African Union.
African heavyweight state Nigeria backed the SADC security committee's call for a postponement, saying it was doubtful a credible poll could be held under current circumstances.
"Clearly Mugabe's plan is to be in a stronger position come negotiating day but the whole process lacks legitimacy both locally and internationally," said John Makumbe, a political analyst and long-time Mugabe critic.
Zimbabweans had hoped the run-off would help end a severe economic crisis marked by acute shortages of foreign currency, food, an 80 percent unemployment rate and the world's highest inflation rate, estimated to be two million percent.
A loaf of bread now costs 6 billion Zimbabwe dollars, or 150 times more than at the time of the first round of elections.
The MDC says nearly 90 of its supporters have died in political violence which it blamed on ZANU-PF supporters. Mugabe says the opposition has been responsible for the violence.
Tsvangirai said if Mugabe declared himself president he would be shunned as an illegitimate leader who killed his own people.
The MDC said it feared ZANU-PF would force people to vote, especially in rural areas, ruling party strongholds where Mugabe seemed to have lost his support to the MDC during the first round of voting in March.
"What will happen tomorrow is that people will be forced to vote ... because the military were mobilised to accompany this process," Tsvangirai said in an interview on Thursday with Portuguese radio station Renascenca.
Zimbabwean police said Britain and the United States were backing plans by the MDC and some NGOs to disrupt Friday's vote with violence, including burning down voting tents.
Since the March election, Mugabe has rallied his shock troops, veterans of the 1970s independence war and youth militia, in a violent campaign that critics say has made a free and fair election impossible.
