Gen Nkunda says he is protecting fellow Tutsis from attack by Hutus
The Democratic Republic of Congo government has agreed to a long-standing rebel demand for talks, to start on Monday, officials say.
Until now, the Congolese government has refused calls for direct talks with General Laurent Nkunda's forces.
Their advance in recent months has forced some 250,000 people from their homes, sparking a humanitarian crisis.
DR Congo and Rwanda also agreed to take action against Rwandan Hutu FDLR rebels based in DR Congo.
FDLR chairman Ignace Murwanashaka told the BBC that if military force was used against them, they would be prepared to fight back.
Rwanda is accused of backing Gen Nkunda, who is an ethnic Tutsi, like many in the Rwandan government.
Gen Nkunda says he is protecting his Congolese Tutsi community from attack by the FDLR, some of whose leaders fled to eastern DR Congo after the 1994 genocide of Tutsis and moderate Hutus.
Both Rwanda and Gen Nkunda have accused the Congolese government of not doing enough to tackle the FDLR Hutu rebels.
The agreement to hold talks was reached in the eastern Congolese city of Goma, which is surrounded by Gen Nkunda's forces.
FORCES AROUND GOMA
CNDP: Gen Nkunda's Tutsi rebels - 6,000 fighters
FDLR: Rwandan Hutus - 6-7,000
Mai Mai: pro-government militia - 3,500
Monuc: UN peacekeepers - 6,000 in North Kivu, including about 1,000 in Goma (17,000 nationwide)
DRC army - 90,000 (nationwide)
Source: UN, military experts
"A meeting will take place between representatives of the government of DR Congo and the CNDP [Gen Nkunda's National Congress for the Defence of the People] under the auspices of the United Nations and the mediator on December 8 in Nairobi in Kenya," DR Congo's Foreign Minister Alexis Thambe Mwamba said after meeting his Rwandan counterpart Rosemary Museminali.
The talks would seek to "formalise" a ceasefire declared by the rebels last month but since broken by both sides.
The DR Congo government was expected to sign an agreement to take action against the FDLR, in exchange for Rwanda agreeing to use its influence over Gen Nkunda to help end the fighting in eastern DR Congo.
Correspondents say similar agreements have failed in the past.
The FDLR fighters have lived in eastern DR Congo since the 1994 slaughter of 800,000 ethnic Tutsis and moderate Hutus and have been a key factor in destabilising the region.
Gen Nkunda has made the disarmament of the Hutu forces a central demand for halting his rebellion, which has led to a humanitarian disaster in the region.
Despite agreeing a ceasefire in November, his forces have continued to attack FDLR forces, saying the truce does not apply to operations against foreign militia.
Rwanda has always strongly denied accusations that it backs Gen Nkunda, but its Tutsi-led government has twice invaded DR Congo in recent years in an attempt to drive out FDLR forces.
The Congolese government has often promised to stop Hutu forces from using its territory, but has not done so.
Its forces have instead been accused of working with the FDLR to exploit the region's rich mines.
In last year's Nairobi agreement, the FDLR forces - estimated to number more than 6,000 - were meant to have been disarmed by the end of August.
That deadline was missed and Gen Nkunda's forces resumed fighting.