The UN Security Council cancelled its first meeting on the conflict in Ethiopia's dissident Tigray region that was due to be held Tuesday, diplomatic sources said.
South Africa, Niger, Tunisia and Saint Vincent and the Grenadines withdrew their request for the behind-closed-doors discussion because envoys have not yet travelled to Ethiopia, said one African diplomat.
"It is necessary to allow more time for the regional efforts that are being undertaken in this regard," he told AFP.
The African Union announced on Friday that three former presidents had been appointed as special envoys to Ethiopia to help mediation efforts between the conflicting parties.
Forces loyal to Tigray's ruling party have been battling Ethiopian soldiers for nearly three weeks, sparking a refugee exodus, civilian deaths and fears of broader instability in the Horn of Africa.
Ethiopia's Prime Minister Abiy Ahmed has ordered the leaders of the northern region of Tigray to surrender ahead of a threatened all-out assault on its capital, Mekele.
Abiy launched the military campaign against the Tigray People's Liberation Front (TPLF) on November 4, accusing it of attacking two federal military camps in the region, and of seeking to destabilize his government.
Hundreds of people are reported to have been killed, but a communications blackout has made claims from both sides difficult to verify.
UN chief Antonio Guterres last week called for the opening of humanitarian corridors to assist civilians caught in the fighting, noting that authorities had so far rejected attempts at mediation.
"We are very worried about the situation in Ethiopia," the secretary general told reporters in New York, warning of a "dramatic humanitarian impact" including in neighboring Sudan.
"We have been asking for the full respect of international humanitarian law and also for the opening of humanitarian corridors and the truces that might be necessary for humanitarian aid to be delivered," he said.
Over 40,000 Ethiopians have fled to neighboring Sudan, the UN's refugee agency said Monday.