On Tuesday, US Secretary of State Antony Blinken said Washington was very concerned about reports that Rwanda had provided support to M 23 rebels in the neighbouring Democratic Republic of Congo.
Blinken said during his visit to Kinshasa ahead of a trip to Rwanda that all parties should halt any support for or cooperation with M 23 or other non-state armed groups.
Blinken said the conflict in eastern Congo was a focus of his meeting with Congolese President Felix Tshisekedi on Tuesday and would be central when he meets Rwandan President Paul Kagame on Wednesday.
The M 23 insurgency is part of the fallout from the 1994 genocide in Rwanda. The group was formed in 2012, claiming to defend Congolese Tutsis, Kagame's ethnic group, against Hutu militias.
Since May, M 23 has waged its most sustained offensive in years, killing dozens and displacing tens of thousands of people. A UN group of experts said that it controlled a territory in Congo almost three times as large as it did in March.
Rwanda has denied accusations from the Congo's government that it supports M 23 and has sent troops into the country. M 23 has denied it receives Rwandan support.
At a joint press conference with Congo's Foreign Minister Christophe Lutundula, Blinken said that he also discussed reforms to Congo's mining sector and US concerns over the auction of oil and gas exploration blocks close to sensitive rainforest and wetland areas.
The United States and Congo agreed on Tuesday to set up a working group to discuss the environmental impact of the auctions.
Lutundula said that the Congo had to find a balance between the need to support its people and economy and its commitment to protecting the environment because of the oil and gas blocks.
He said that we stand firm on this commitment.