In September, during protests organised by the Gathering against the delayed elections, 53 people were killed
Leaders or their representatives from the Economic Community of Central African States (ECCAS) met in Libreville, the capital of Gabon.
"The conference called on those political and social forces (in DRC) which have not yet done so to join the October 18, 2016 political agreement, which is aimed at strengthening social cohesion and the holding of calm democratic elections," a statement said.
DRC President Laurent Kabila, whose tenure is scheduled to end December 20, has been elected to two terms and is barred from serving again but has never said he plans to step aside.
In October, he cut a power-sharing deal under a national "dialogue," appointing fringe opposition politician Samy Badibanga as prime minister in a move that analysts say effectively extends his term to at least late 2017.
The "Gathering", a movement of mainstream opposition groups that back politician Etienne Tshisekedi to replace Kabila, has rejected the deal.
In September, during protests organised by the Gathering against the delayed elections, 53 people were killed, according to a UN toll.
Of the 11 countries taking part in Wednesday's meeting, four were represented by heads of state -- presidents Idriss Deby Itno of Chad, Paul Kagame of Rwanda, Faustin-Archange Touadera of Central African Republic (CAR) and the meeting's host, Ali Bongo Ondimba of Gabon.
The statement also said ECCAS intends to "deploy a mission" in the strife-torn former French colony of CAR "to support post-conflict reconstruction efforts."