Rwanda and the Democratic Republic of Congo held a fourth day of peace talks in South Africa Sunday. Officials are optimistic about reaching an agreement soon.

South African Deputy President Jacob Zuma is chairing the talks in Pretoria. He has issued a statement saying a lot of progress has been made since they began Thursday.

He says the two sides are meeting in an "amicable and constructive atmosphere, and both delegations remain optimistic a solution will be found."

A spokeswoman for Mr. Zuma told VOA it is not clear when the talks will end. She says the deputy president is prepared to keep the negotiations going until the two sides reach an agreement.

Few other details of the talks are available through official channels, but regional experts and sources close to the talks say there are several key issues on the table.

One is the creation of a buffer zone between Rwanda and the DRC. Another, related issue is the fate of the former Rwandan soldiers and extremist Hutu militants known as Interahamwe, who took part in the 1994 Rwandan genocide and continue to operate out of eastern Congo.

Kigali has long accused the DRC government of backing the militants. Rwanda says it will not withdraw its estimated 20,000 troops from the DRC until the Interahamwe no longer pose a threat to its national security.

Kinshasa has demanded a withdrawal of the Rwandan troops before it will take action against them.

The Pretoria talks began after a rare meeting between Rwandan President Paul Kagame and Congolese leader Joseph Kabila. The two men met in Durban earlier this month during the launch of the African Union.

The Congolese and Rwandan ministers in the presidency are leading their respective delegations in Pretoria. The two sides have also been joined by representatives from the United Nations and from the main Rwanda-backed rebel group, the Rally for Congolese Democracy.

The talks are expected to continue at least through Monday as negotiators edge closer to a deal.