Fighters from Congo's M23 rebellion are the biggest challenge to government troops and U.N. peacekeepers in the eastern Kivu provinces of the Congo.
U.N. Secretary General Ban Ki-moon said earlier this week that the rebel attacks include violence against women and children.
"The extent of violence and human suffering in eastern DRC is overwhelming. I deplore the recent military activities of the M23 and the other armed groups in eastern DRC," said Ban.
African leaders meeting at the United Nations are backing peace talks in Uganda, but the talks are complicated by persistent reports of Rwandan support for the rebels. The United States is among those who have called on Rwanda to stop their support.
"We reiterate our call for Rwanda to cease any and all support to the M23 and to respect DRC’s territorial integrity, consistent with UN Security Council resolutions," said U.S. State Department spokeswoman Marie Harf.
By publicly accusing a U.S. ally of backing the M23 rebels, the Obama administration is making a bold move, says Sarah Margon of Human Rights Watch.
"They've told the Rwandans we're putting you on notice. But what next? And so if the Rwandans don't stop, what will the U.S. be willing to do?" wondered Margon.
Rwandan President Paul Kagame denies involvement and says the international community shouldn't focus on M23 rebels when there are so many other groups contributing to instability in the eastern regions of the Congo.
The peace talks in Kampala have focused on other armed groups as well.
In an interview with VOA, U.S. Special Envoy to the region Russ Feingold said that focusing on all the involved groups is the only way forward.
"Whatever happens with the Kampala talks, the framework and the peace process involving the countries in the region goes on and will deal with the root and fundamental problems, not just the issue of M23," said Feingold.
Nonetheless, achieving the more immediate goal of stopping the fighting requires focusing on the M23, said Ugandan Foreign Minister Sam Kutesa.
"M23 should put an end to all military activities and stop war and threats of overthrowing the lawful government of the DRC," Kutesa declared.
President Joseph Kabila's troops are moving to re-establish central authority over eastern Congo, but Margon expects no end to challenges in the area.
"Without Rwanda ceasing to provide support for the M23, many of the other elements, whether it be the upcoming elections in Congo, Congo's extension of governing authority in the east, regional development, are not going to be able to happen," said Margon.
In the past, the rebels have been integrated into Congo's military as part of an attempt at reconciliation. This time around, Congolese officials say the worst of the M23 leaders will not be granted amnesty in any new peace deal.