The M23 rebel movement active in the troubled east of the Democratic Republic of Congo said Thursday it would only resume peace talks if the government signs up to a ceasefire.
M23 political leader Bertrand Bisimwa told AFP that DR Congo government forces and the Hutu rebel group the Democratic Forces for the Liberation of Rwanda (FDLR) were advancing on two fronts "and we don't know what their intentions are."
"Our delegation will return to Kampala if -- and only if -- the government agrees to sign a ceasefire with us immediately, " he said.
The M23, which has been fighting the army in the volatile east since May last year, triggered a new crisis in November when it occupied the key town of Goma for more than a week before withdrawing under regional mediation.
The group's ultimatum Thursday came shortly after a visit by the new UN special envoy for Africa's Great Lakes region, former Irish president Mary Robinson.
Robinson, who is on a regional tour leading political efforts to bring an end to more than two decades of conflict in the mineral-rich region, on Tuesday voiced "shock" over the scale of human rights abuses there.
The United Nations brokered a February peace accord signed by 11 African states and the following month the Security Council approved the creation of a new brigade to help the UN mission in DR Congo.
Under the accord, the 11 states vowed not to interfere in the affairs of their neighbours, and DR Congo President Joseph Kabila promised democratic advances and improved security.
The M23, which Kinshasa and a panel of UN experts say was created as a Rwandan proxy, is accused of a number of rights abuses and has been slapped with UN sanctions.
Both Rwanda and Uganda have been accused of backing rebel groups in the region.