The United Nations, African Union, European Union and the International Organisation of the Francophonie "are increasingly concerned by the continuing impasse in the dialogue among the political stakeholders" in DRC, a joint statement said.
The talks aim to implement a power-sharing deal signed on New Year's Eve by the government and the opposition to end a political crisis over President Joseph Kabila's fate.
Kabila's second and final mandate ran out in December but elections did not take place.
In addition, a prime minister was to be named from the opposition ranks.
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But Tshisekedi's death two weeks ago has complicated an already strained situation as politicians vie for the top spot.
"This situation has the potential to undermine the political goodwill that led to the signing of the 31 December agreement," the statement said.
They called on the stakeholders "to redouble, in good faith, their efforts towards a speedy conclusion of the ongoing talks."
The four partner organisations said the agreement "is critical in upholding the legitimacy of the transitional institutions until elections.