Further delays are expected because of legal manoeuvres and a recount of 23 constituencies ordered by the ZEC for next Saturday. The MDC is challenging that decision in court.
The MDC also filed on Monday an application asking the electoral court to set aside the results in about 60 parliamentary seats won by Mugabe's ZANU-PF.
"All in all we have filed about 60 applications to the Electoral Court in respect of the house of assembly seats. The applications are to ensure that the declarations of the results be set aside," MDC lawyer Charles Kwaramba told Reuters.
In its court challenge the MDC accuses ZANU-PF of vote-buying, intimidating and interfering with presiding election officers and other malpractices, Kwaramba said.
ZANU-PF says neither Tsvangirai nor Mugabe won an absolute majority in the presidential vote, making a run-off necessary.
The delays have stoked tension and brought a chorus of Western condemnation.
Both MDC and international human rights organisations say Mugabe has unleashed militias in a campaign of violence to intimidate opposition supporters ahead of a runoff.
The MDC says hundreds of villagers have been forced out of their homes by militia attacks. A quarter of Zimbabwe's population has fled to escape chronic shortages of food and fuel and 80 percent unemployment.
The ZEC's recounts could overturn the MDC's victory in the parliamentary vote, Mugabe's first defeat since taking power after independence from Britain in 1980.
MDC lawyer Selby Hwacha accused the ZEC of calling the recount to help ZANU-PF rig the poll.
The summit of SADC (Southern African Development Community) in Lusaka at the weekend urged Mugabe to ensure any run-off would be held "in a secure environment".
The former guerrilla commander did not attend.
