Zimbabwean President Robert Mugabe, in power since 1980, appeared optimistic that an agreement could be reached but Tsvangirai warned of regional instability if the ruling party refused to loosen what he called its illegitimate grip on power.
The old foes have been deadlocked over allocation of important cabinet positions since the Sept. 15 deal, which Zimbabweans hoped would produce a united leadership to revive the ruined economy in the country where inflation is the world’s highest and food and fuel shortages widespread.
In a speech to Southern African heads of state, Tsvangirai suggested his Movement for Democratic Change (MDC) would only accept a comprehensive agreement that gives his party a fair share of powerful ministries.
"Only a genuine power-sharing arrangement will allow the MDC to join a new government because that is our mandate from the people of Zimbabwe and we cannot and will not betray their hopes and dreams for a better future," he said in the speech, a copy of which was seen by Reuters.
One of Tsvangirai’s demands to the summit was "imposing a deadline on the agreement" for formation of a new cabinet.
The 15-nation Southern African Development Community (SADC), meeting in Johannesburg, is trying to end the impasse.
"Good progress is being made. It’s going well," Mugabe told reporters, without elaborating.
Highlighting growing regional impatience, South African President Kgalema Motlanthe said the deal offered the only hope for Zimbabwe to ease the economic crisis.
Past SADC meetings have failed to produce a breakthrough.
Although some leaders have taken a tough line on Mugabe, political analysts say the SADC did not have the resolve to impose tough measures, such as sanctions, to force an agreement.
The heads of state of Botswana and Zambia, the most outspoken regional critics of Mugabe, did not attend the summit.
Tsvangirai, who would become prime minister under the power-sharing deal, has accused Mugabe’s ZANU-PF of trying to seize the lion’s share of important ministries and relegating the MDC to the role of junior partner.
Tsvangirai said no agreement had been reached on the 10 most important ministries.
He proposed a trade off of ministries, with one party getting the interior ministry and the other defence, for instance, according to the copy of the speech.
Tsvangirai warned of dire consequences if Mugabe refused to agree to a fair deal.
"If this does not happen and ZANU-PF refuses to loosen its illegitimate grip on power, this impasse will continue, the suffering will worsen and Zimbabwe’s collapse will threaten the stability of the enitire region," he said in the speech.
Zimbabwe’s economic crisis has forced millions of its citizens to flee the country, many of them moving to neighbouring South Africa, Africa’s biggest economy.
Zimbabwean state media reported earlier that Mugabe’s government would not change its stance on key cabinet positions and the opposition should accept joint control of the interior ministry.
"We hope the parties will show political maturity by putting the interest of the people of Zimbabwe first," Motlanthe, whose country is the current SADC chair, said in his opening remarks.
Tsvangirai’s MDC said last week that Mugabe’s ZANU-PF party had put a "full stop" to negotiations on forming a government by engaging in what it said was widespread violence.