Negotiations between the Democratic Republic of Congo government and armed groups in the east to sign a peace pact have stalled in Goma.
General Laurent Nkunda called for a ceasefire in December
Observers said representatives of rebel general Laurent Nkunda had taken issue with parts of an agreed draft document.
The deal would include an immediate ceasefire, the phased withdrawal of all rebel forces in North Kivu province and resettlement of thousands of villagers.
Conflict in the country is estimated to have claimed 5.4m lives since 1998.
The different factions had said they were ready to demobilise after seeing the peace deal on Monday but then disagreements emerged.
In addition to Gen Nkunda's issues with the deal, there were objections to disarming from one of seven groups that make up the Mai Mai militia.
Talks involving the DR Congo government and more than 20 rebel groups have been under way for more than two weeks.
The conference is being sponsored by the United States, the European Union and the African Union.
The deal aims to end months of bloody conflict around the eastern city of Goma, which has driven close to half a million people from their homes in the last year.
War and related crises in the central African country is claiming 45,000 lives a month, according to an aid agency.
The International Rescue Committee says the death toll in the past decade has surpassed any conflict since World War II.
The deal would grant amnesty to all fighting groups, but it is not clear what will happen to Mr Nkunda, who has not attended the talks.
There has been talk that Gen Nkunda could be integrated into the army or sent into exile.
He leads the main rebel movement in the area and his forces repulsed a major government offensive last December.
The government has issued an international arrest warrant against Gen Nkunda, for alleged war crimes committed by his forces.
He claims his forces are protecting ethnic Tutsis in North Kivu from Rwandan Hutu rebels, who have lived in eastern DR Congo since the Rwandan genocide in 1994.