The Congolese governement has refused to negotiate with the rebels, who have been fighting government troops in the eastern Nord-Kivu region.
On Sunday the United Nations mission in Kinshasa urged Nkunda's men to immediately demobilise.
On Wednesday Nkunda proposed a truce after at least 85 of his forces died in heavy clashes, and offered 500 of his men for demobilisation.
This was greeted with caution in Kinshasa.
The UN peacekeeping mission in DR Congo (Monuc) said in a statement on Sunday: "Monuc urges all dissident troops to join 'brassage' immediately, for which Monuc, with the government of the Democratic Republic of Congo, have already made the necessary arrangements, including reception sites and transport."
Joseph Kabila, the president, arrived on Sunday in the Nord-Kivu capital of Goma, airport sources said. The visit was unscheduled and it was unclear how long he would stay.
Since September 24, Nkunda's men have battled at least 15,000 government troops in Nord-Kivu in breach of a September 6 ceasefire mediated by Monuc.
Nkunda, a Tutsi, says he is protecting the minority local Tutsi population and accuses the DR Congo army of colluding with Hutu rebels hiding out in the area since the end of the Rwandan genocide in 1994.
Nkunda said: "In Congo now, the former Hutu rebels from Rwanda are mixed with the government forces. We fear that they are going to kill Tutsis.
"We have many evidences, documents that we are releasing to the UN forces in Congo tomorrow."
UN organisations in Kinshasa have warned of a humanitarian crisis as hundreds of thousands of people flee the fighting and flood into already overcrowded camps.
The fighting has uprooted more than 370,000 people from their homes in less than a year, according to UN estimates, bringing to 750,000 the total number of displaced people in the restive eastern province.