A meeting on Monday ended after less than an hour when representatives from the DR Congo and its main ally, Zimbabwe, said they were not satisfied with several points in the draft.

The BBC's Ishbel Matheson: Tough words for the warring parties

The sticking points appeared to include the formation of verification committees to oversee the peace process, the withdrawal of foreign troops, and the setting up of institutions to promote dialogue with rebel groups.

One of the organisers, Southern African Development Community Secretary-General Kaire Mbuende, said the ministers would stay in Lusaka "even for a month" until agreement was reached. He told reporters the differences between the parties had now been narrowed to ones of protocol rather than substance.

The proposed agreement, which was hammered out by negotiators after several days of talks, seeks to bring to an end 10 months of civil war.

It is reported to call for:

• A ceasefire from 3 July
• Deployment of peacekeepers
• Withdrawal of foreign armies
• Disarming of rebel groups

Heads of State

If discussions by ministers are eventually successful, heads of state from the region will gather to put their signatures to a ceasefire agreement.

The talks have brought together representatives of all sides in the civil war, which has pitted several rebel groups against the government forces of President Laurent Kabila.

The rebels are backed by Rwanda and Uganda, while President Laurent Kabila has been supported by Zimbabwe, Namibia and Angola.

On Friday, the Rwandan President, Pasteur Bizimungu, said he would sign the agreement only if it guaranteed the security of his country's borders.

He said Rwanda would stop fighting if there was no further threat from Hutu militias operating from Congolese territory.