Warring rebels and militias in eastern Democratic Republic of Congo signed a cease-fire deal on Wednesday aimed at ending conflict at the heart of one of the world's most deadly humanitarian catastrophes.

The peace pact in the eastern town of Goma was signed by Tutsi rebels loyal to renegade Gen. Laurent Nkunda, President Joseph Kabila's government, and several militia and armed groups from Congo's North and South Kivu provinces.

While foreign observers welcomed the deal as a chance for lasting peace in Congo, they warned its implementation could be difficult after the collapse of several previous cease-fires.

"We have indeed won a great battle over the sceptics," Kabila told the closing ceremony of a peace conference in the capital of North Kivu, Goma.

"We are not, however, at the end of our troubles. A new challenge rises up before us, a greater and more difficult challenge than yesterday's: the challenge of implementation."

The pact was the fruit of more than two weeks of intense negotiations between the warring parties in Congo's turbulent eastern borderlands, where conflict has raged on for years despite the formal end of the country's 1998-2003 war.

The White House welcomed the signing of the peace agreement and called on all sides to ensure its terms were implemented quickly.

"The United States, working with the international community, will continue to actively support the Congolese government's commitment to achieve peace and prosperity in eastern Congo," the White House said in a statement.

The United Nations and Western governments had pressed Kabila, Nkunda and militia leaders to make peace. Congo's size and location make it key for stability at the heart of Africa.

A former Belgian colony, Congo is a treasure chest of strategic minerals coveted by both the West and China, such as copper, gold, diamonds, uranium and coltan, which is used in mobile phones and other consumer electronic products.

A survey published this week by the International Rescue Committee aid group said Congo's war and its lingering aftermath had killed 5.4 million people, the highest toll of any conflict since World War Two. It said 45,000 Congolese were still dying each month, most from conflict-related disease and hunger.

IMMEDIATE CEASE-FIRE

The agreement establishes an immediate cease-fire and the creation in five days of a buffer zone to be patrolled by U.N. peacekeepers in North Kivu province, the scene of heavy fighting in recent months between Nkunda's rebels and government troops.

"This is a very important milestone for peace in eastern Congo," Anneke Van Woudenberg, senior researcher for New York-based Human Rights Watch, told Reuters. "But it's only the beginning and the road ahead will be difficult."

Under the deal, a technical commission will be set up to oversee disarmament of the Nkunda rebels and Mai Mai fighters and their integration into the national army, or demobilization.

The government is promising an amnesty law for the Mai Mai and Nkunda rebels covering "insurgency and acts of war."

But analysts said one outstanding issue was that Nkunda's own future was not clearly defined in the peace deal.

"We all know Nkunda will not receive amnesty. That problem is not going away, and they will have to find a way to deal with it," said Henri Boshoff, military analyst with South Africa's Institute for Security Studies.

Implementing the deal may also depend on efforts to rid east Congo of Nkunda's traditional enemies, Rwandan Hutu rebels of the Democratic Forces for the Liberation of Rwanda, or FDLR, who were not invited to the Goma peace conference.

Congo signed an agreement with Rwanda late last year promising to drive out the FDLR, some of whose leaders were responsible for the 1994 Rwandan genocide that slaughtered 800,000 Tutsis and moderate Hutus.

Nkunda led 4,000 fighters into the bush in a 2004 revolt and has justified his rebellion as an effort to protect east Congo's Tutsi minority against attacks by the Rwandan Hutu FDLR.