The MDC is due to go to court later on Sunday to try and force the release of the presidential result, eight days after Zimbabweans voted in parliamentary and presidential elections.
Mugabe's ruling ZANU-PF party, defeated by the MDC in parliamentary elections, has asked the Zimbabwe Electoral Commission to recount the presidential election results, state media reported on Sunday.
But MDC spokesman Tendai Biti said the request for a recount was illegal and "madness".
"Legally they have no right to ask for a recount, they have absolutely no footing to ask for a recount so what they are trying to do is illegal," Biti told Reuters.
"It's madness literally and metaphorically".
Tensions between the two sides have risen sharply since the March 29 elections, fuelled by opposition suspicions that Mugabe is preparing to rig the outcome of the elections to extend his 28-year rule.
Morgan Tsvangirai, leader of the Movement for Democratic Change, again declared victory over Mugabe in the presidential race on Saturday and accused the 84-year-old leader of "preparing a war on the people".
Mugabe's supporters struck back hours later when state media reported ZANU-PF had asked election officials to defer release of the presidential poll results and conduct a recount and audit of all electoral materials, including ballots.
The MDC will ask the High Court in Harare on Sunday to order the results to be issued immediately.
ZANU-PF and independent monitors' projections show Tsvangirai being forced into a presidential runoff after failing to win an absolute majority in the vote.
Top ZANU-PF officials have endorsed Mugabe for the second ballot.
