The electoral commission had earlier in the week extended a deadline for the election to be held from May 23 to July 31.
Tsvangirai had previously said that any ballot held after May 23 would be illegitimate under Zimbabwe’s electoral law and has only reluctantly agreed to contest the run-off.
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He believes that he won enough votes in the first round of voting on March 29 to cross the 50 per cent threshold needed to win the presidency.
The MDC now holds the majority in parliament after defeating Zanu-PF in elections for the legislature, held simultaneously with the presidential poll.