African leaders grappled Sunday with a long-simmering crisis in Zimbabwe and a new humanitarian catastrophe in Congo, lamenting that war and conflict stand in the way of development in the world's poorest continent.

South African President Kgalema Motlanthe opened Sunday's extraordinary summit of the Southern African Development Community with a call for a cease-fire so humanitarian aid can reach those displaced by fighting in eastern Congo.

No breakthroughs were expected during the one-day summit.

Congo's east has been engulfed in recent weeks in fighting involving rebels, government soldiers and pro-government militiamen. The world's largest U.N. peacekeeping contingent has struggled to protect civilians in eastern Congo.

The peace keepers' "current mandate limits their ability to become real peacemakers and provide for a lasting solution," Motlanthe said Sunday.

Congolese President Joseph Kabila attended the Johannesburg meeting of the regional bloc, whose 15 members include sprawling Congo and several of its neighbors. The Congolese delegation sat next to that of Angola, where Kabila had sent an envoy seeking support last week.

Angolan Foreign Minister Assuncao dos Anjos, who led his nation's delegation to Johannesburg, was asked on the sidelines of the meeting about numerous reports of Angolan forces fighting alongside Kabila's troops in east Congo. Dos Anjos said only: "No troops."

A 1998-2002 war in Congo drew in Angola, Zimbabwe and other neighbors. The current violence has roots in the 1994 Rwandan genocide, during which hundreds of thousands of minority Tutsis were slaughtered. Tutsi rebels from Rwanda overthrew the Hutu-dominated Rwandan government in an ensuing civil war. Millions of Hutus fled to eastern Congo, among them armed Hutu militants who set up bases on Congolese soil that remain today.

Today, Congo's army is fighting rebels in the east loyal to Laurent Nkunda, a Congolese Tutsi who claims to be protecting his ethnic group from Rwandan Hutus.

While Congo was at the top of the agenda Sunday, Zimbabwe's crisis has been on the regional bloc's agenda much longer. A year ago, the bloc appointed Motlanthe's predecessor Thabo Mbeki to mediate in the dispute between Zimbabwean President Robert Mugabe and his political opposition.

After two disputed elections and a wave of state-sponsored political violence, Mbeki persuaded the rivals to sign a power-sharing agreement in September. But the agreement has stalled over how to allocate Cabinet posts.

"Peace and stability is a precondition to development," Motlanthe said in the brief, businesslike opening ceremony before the leaders went into closed sessions Sunday. "Any slide into conflict and war will reverse the hard-won gains of the people of our region."

Motlanthe stressed the goal of Sunday's meeting "will be to resolve the issues before it."

The Zimbabwean opposition is pressing leaders at the summit to call for a fair division of Cabinet posts in a proposed unity government. The opposition in particular wants the ministries that control police and finance — posts Mugabe has tried to claim unilaterally for his ZANU-PF party. In his opening remarks Sunday, Motlanthe singled out the police ministry, in charge of officers accused in attacks on the opposition, as contentious.

Mugabe, in power since independence from Britain in 1980, was to remain president under the power-sharing deal, with opposition leader Morgan Tsvangirai as prime minister. With the deal stalled, Zimbabweans are without leadership as their economy collapses. Inflation is the highest in the world; health, education and public utility infrastructure are crumbling; and the U.N. predicts half the population will need food aid by next year.

Mugabe is accused of overseeing a corrupt regime that maintains power through electoral fraud, intimidation and violence. He may fear human rights trials if he yields power, and his supporters would lose their access to his treasury.

The opposition, meanwhile, is accused by some of its supporters of giving up too much by allowing Mugabe to remain president and by agreeing to a power-sharing arrangement that is unlikely to run smoothly because of distrust on both sides.

"We don't want any unity with Mugabe," said Thembi Moyo, a 40-year-old actress from southern Zimbabwe who joined about 500 opposition protesters outside the conference hall where the summit was being held Sunday.

A much smaller crowd of Mugabe supporters also gathered.