The US has accused Rwanda of breaking a US-brokered peace agreement by supporting a violent rebel attack in eastern Congo. The rebel group M23, backed by Rwanda, has killed more than 400 civilians since their offensive escalated in South Kivu province. Officials say Rwandan special forces are in the strategic city of Uvira. US Ambassador to the UN Mike Waltz called Rwanda "leading the region towards increased instability and war." He warned the UN Security Council that the US will hold "spoilers to peace" accountable. Waltz urged Rwanda to respect Congo's right to defend its land and allow forces from Burundi to assist Congo. This violence comes despite a recent peace deal signed in Washington by Congo’s and Rwanda’s presidents. The deal required Rwanda to stop aiding armed groups like M23 but did not include the rebels themselves. M23 captured Uvira, Congo's last major stronghold in South Kivu, after a swift attack starting in early December. Uvira lies on Lake Tanganyika's northern tip, near Burundi's city of Bujumbura. The rebels now control a wide area in eastern Congo. The conflict has displaced about 200,000 people. Refugees are crossing into Burundi, and gunfire has threatened Burundian border towns, raising fears of wider regional conflict. M23, one of more than 100 armed groups in eastern Congo, grew from hundreds of fighters in 2021 to around 6,500 members now, with alleged Rwandan support. UN experts say Rwanda provided training and fought alongside M23, with 5,000 to 7,000 troops present. Congo’s Foreign Minister Thérèse Kayikwamba Wagner called for UN sanctions against Rwandan leaders and a ban on mineral exports from Rwanda. Rwanda is a major UN peacekeeping troop contributor with nearly 6,000 soldiers. Eastern Congo’s rich minerals are key to global industries, and the US is keen to secure access outside of China's influence.