HARARE, Zimbabwe (CNN) -- Opposition leader Morgan Tsvangirai expressed frustration Wednesday at deadlocked talks over a power-sharing agreement with Zimbabwean President Robert Mugabe.
Leaders from four southern African nations who have been mediating the stalled dispute called Tuesday for a full Southern African Development Community summit.
Mugabe's ZANU-PF party and Tsvangirai's MDC party have been negotiating over the distribution of cabinet posts in a unity government.
"The situation is desperate. People are suffering," Tsvangirai told CNN Wednesday. "It is very frustrating, but what can we do? We cannot have a shared burden with ZANU-PF of being responsible for the suffering of the people."
Tsvangirai said he hopes the SADC summit will break the deadlock and ensure a fair deal.
"I cannot determine their capacity to break the deadlock," the MDC leader said. "They have told us that they can do it and we are looking forward to the summit. All we want is a fair deal."
The SADC troika -- Angola, Mozambique and Swaziland -- failed, along with South Africa, to overcome a dispute between Mugabe and Tsvangirai over who would control the Ministry of Home Affairs, the troika said in a statement Tuesday.
South Africa is the designated regional mediator in the Zimbabwe crisis.
The troika did not indicate when or where the full summit meeting of the 15 SADC members would occur.
Despite the troika's statement, MDC Secretary-General Tendai Biti said the disagreement extends beyond the Ministry of Home Affairs.
"The entire gamut of ministries is still open, contrary to the widely publicized view that it is only one ministry that is still outstanding," he told reporters.
There was no response from the Mugabe's ZANU-PF party.
In addition to the ministries, Biti wrote in a statement posted on the MDC Web site, other issues remain unresolved. They include the appointment of diplomats in Zimbabwe's foreign mission and a constitutional amendment that would put into effect the September 15 power-sharing deal that Mugabe and Tsvangirai signed.
"It is clear that there is so much that still has to be done," Biti wrote. He said his party remains committed to the agreement.
Under the power-sharing deal, brokered by former South African President Thabo Mbeki, Tsvangirai would become prime minister and Mugabe would remain president. Arthur Mutambara, who leads a splinter MDC faction, would become deputy prime minister.
Since the deal was struck, however, the two sides have argued over who should control which ministries.
The negotiations with the SADC leaders had been scheduled to take place in Swaziland, but the MDC alleged Tsvangirai could not attend because he could not get the necessary travel documents from the government in time.
The September 15 agreement was to end months of turmoil and violence that followed the country's March presidential elections.
Tsvangirai garnered the most votes then, but did not win enough to avoid a runoff with Mugabe, who has ruled the country since its independence from Britain in 1980.
The MDC leader withdrew days before the June 27 runoff, alleging that Mugabe's supporters had waged a campaign of violence and intimidation against opposition supporters. He said he could not participate in the election, which he condemned as a "sham."