The opposition Movement for Democratic Change says its candidate, Morgan Tsvangirai, won the March 29 vote outright, and accused Mugabe of delaying the results so he can orchestrate a runoff and give ruling party militants time to intimidate voters and ensure he wins a second election.
With no resolution in sight, Zambian President Levy Mwanawasa called an emergency summit of the Southern African Development Community for Saturday to discuss the crisis.
"Such meetings are usually very healthy so heads of state can brief each other, not only us in Zimbabwe," Zimbabwean Information Minister Sikhanyiso Ndlovu told The Associated Press.
But he said the meeting wasn't necessary. "There is no crisis in Zimbabwe that warrants a special meeting on Zimbabwe," he said.
Mwanawasa originally planned to send a delegation of former heads of state to Zimbabwe but decided to hold an urgent summit instead because the situation had grown so serious, Zambian state radio reported.
Deputy Information Minister Bright Matonga confirmed Mugabe would be at the meeting.
"If there is a SADC meeting of heads of state, then obviously he will attend," he told the AP.
Tsvangirai also will also attend the summit, said MDC spokesman Nqobizitha Mlilo.
"He is a head of state himself as well," Mlilo said, reiterating the opposition's insistence that Tsvangirai won the election.
Tsvangirai, who was traveling throughout the region to ask Mugabe's peers to push him to end the standoff, was headed Thursday to South Africa to meet with President Thabo Mbeki, Mlilo said.
He intends to "impress upon President Mbeki that Mugabe must concede defeat," Mlilo said. Tsvangirai will head to Zambia on Friday in advance of the summit, he said.
Mbeki's spokesman Mukoni Ratshitanga said he could not confirm the men would meet.
As part of his regional tour, Tsvangirai met Wednesday with Botswana President Seretse Ian Khama.
"Definitely I think the Botswana president was very helpful to us ... he would also like to participate in assisting in whatever way he can to resolve the crisis," Tsvangirai aide George Sibotshiwe said.
African leaders previously deferred to Mbeki and his strategy of "quiet diplomacy" on dealing with Zimbabwe. Mwanawasa has stood out as the only southern African leader to publicly criticize Mugabe's policies, last year likening the country's economy to "a sinking Titanic."
MDC secretary-general Tendai Biti said regional leaders should push for Mugabe's resignation.
"We don't know why the world has to wait until dead bodies start littering the streets of Harare," he said Wednesday. Biti hinted that the opposition would boycott any runoff.
"Morgan Tsvangirai won this election without the need for a runoff, and we will not accept any other result except one that confirms that we won this election," he said.
The High Court will decide Monday whether to grant an opposition request for the election results to be released, lawyers for the MDC and the election commission said.
Mugabe has virtually conceded he did not win the election and appeared to be campaigning for a runoff by intimidating his foes and fanning racial tensions.
Biti accused the ruling party of deploying senior army and police officials across the country to "oversee the reversal process."
Desmond Mufunde, a newly elected MDC councilman from the rural Gweru district, said soldiers attacked some people in his district last weekend.
Zimbabwe's Commercial Farmers' Union accused ruling party supporters of forcing dozens of white farmers off their land and ransacking their homes. Farmers warned that continued chaos could endanger the wheat crop, vital to a nation that has grown deeply dependent on food aid during the worsening economic crisis.
"The planting for wheat will be in a few weeks time and if it is not in, we'll go starving again," said farm union spokesman Mike Clark.
The U.S.-based National Democratic Institute said Wednesday that one of its staff members was held by authorities for six days.
Dileepan Sivapathasundaram, a U.S. citizen who had been working with local groups monitoring election monitors, was detained at Harare's airport as he tried to leave the country last Thursday, the nonprofit group said. He was freed and since has left the country.