Democratic Republic of Congo's President Felix Tshisekedi and his Rwandan counterpart Paul Kagame are due to begin talks in the Angolan capital Luanda on Wednesday amid tensions over a surge of rebel attacks in eastern Congo.
The two neighbours have been locking horns since the M23 rebel group began a major offensive in Congo's eastern borderlands at the end of March.
Congo accuses Rwanda of backing the group. Kigali denies this, and in turn accuses Kinshasa of fighting alongside another armed group intent on seizing power in Kigali.
Tshisekedi arrived in Luanda on Tuesday for a "mini tripartite summit" on peace in the Congo on Wednesday, the presidency said in a statement, describing the meeting as a moment "of truth".
Rwanda's ambassador in Congo Vincent Karega told Reuters Kagame had also arrived.
The M23 have seized an important border post in their most sustained offensive since capturing swathes of territory in 2012-2013.
Congo's army is battling to push them out of newly gained positions close to eastern Congo's main city of Goma.
The fighting has forced tens of thousands to flee their homes in an area that has had little respite from conflict since Rwanda and neighbouring Uganda invaded in 1996, citing threats from local militia groups.
Despite billions of dollars spent on one of the United Nations' largest peacekeeping forces, more than 120 rebel groups continue to operate across east Congo almost two decades after the official end of the central African country's civil wars.
Angolan President Joao Lourenco has been appointed by the African Union to mediate the talks and restore dialogue between the two parties.
(Reporting by Stanis Bujakera; Writing by Sofia Christensen; Editing by Hereward Holland and Alison Williams)
