Rebels are advancing on the eastern Democratic Republic of Congo city of Goma after pushing back United Nations peacekeepers and government troops in recent fighting.
Rebel spokesman Vianney Kazarama said M23 fighters are just a few kilometers from Goma. He said they are ready to respond to an attack by the army and repel it from the city if provoked.
Fighting between rebel and government forces have forced thousands of people to flee their homes.
On Saturday, U.N. attack helicopters targeted rebel positions as U.N. Secretary-General Ban Ki-moon urged Rwandan President Paul Kagame to use his influence on the M23 to help calm the situation.
Most members of M23 group are former Congolese soldiers who defected earlier this year, demanding better pay and weapons.
The United Nations Security Council held a closed-door emergency meeting Saturday at France's request to discuss the fighting.
The renewed violence coincides with the release of a United Nations report repeating accusations that elements in neighboring Rwanda and Uganda are supporting the rebels.
Rwanda and Uganda have strongly denied they are supporting the M23. Uganda has said if the United Nations does not withdraw the allegations, it may remove its soldiers from international peacekeeping missions, including the one in Somalia.