U.S. Secretary of State Marco Rubio told Rwandan President Paul Kagame on Tuesday that Washington was "deeply troubled" by escalation in the conflict in the Democratic Republic of Congo, particularly the fall of the city of Goma to Rwandan-backed rebels.

Rwanda, which diplomats say backs M23 fighters who seized Goma in Democratic Republic of Congo this week, called on Wednesday for a ceasefire across eastern Congo and for Congo to negotiate with the rebels while denying Rwandan troops were involved.