Congolese rebels have said they will defy a deadline to leave the strategic eastern city of Goma and will fight to hold it.
A spokesman for the M23 group called it "a declaration of war" and said the army will resume combat.
M23 president Jean-Marie Runiga said the rebels will not leave the city of a million people which they seized a week ago. The deadline imposed by the International Conference on the Great Lakes Region for the rebels to depart was midnight on Monday.
Mr Runiga said that the M23 now had 1,000 tons of arms and ammunition, including heavy artillery, abandoned by the fleeing Congo army.
But he also said that the rebels would like to negotiate with the Congolese government. In April, when the rebellion began, the group initially said they wanted to revisit the March 23, 2009 peace accord which paved the way for the fighters to join the Congolese military. The group initially claimed that Congo had not held up its end of the bargain, failing to provide the fighters with adequate pay and proper equipment.
Congo has already said that they are willing to negotiate with M23 on the basis of the 2009 peace accord, but Mr Runiga said that they no longer want to talk about only that. "Lots happened between 2009 and 2012. It is better to tackle the root causes of the issue once and for all," he said.
He said that for the armed group to leave Goma, Congo is going to have to agree to a new set of conditions.
The United Nations Group of Experts say M23 are financed by Rwanda, which is providing them with arms, sophisticated communications equipment as well as several battalions of troops.
"They have refused to leave the city of Goma. This is a declaration of war, and we intend to resume combat," said Congo's military spokesman.
The M23 was created nearly eight months ago by former rebels who joined, and then defected from the Congolese army. They have been accused of human rights abuses, including executions and forced recruitment of children.