Ukrainian representatives and pro-Russian rebels will not be meeting in the Belarussian capital Minsk on Friday for what Kiev had hoped would be the signing of a final peace deal, a Belarussian official said.
"There will be no contact group meeting today," Belarussian foreign ministry said spokesman Dmitry Mironchik told AFP by telephone.
The so-called Trilateral Contact Group on Ukraine also includes mediators from Russia and the Organization for Security and Co-operation in Europe (OSCE).
The warring sides reported a tense day of inital negotiations on Wednesday that made little progress toward a final peace accord.
The ministry spokesman added that "Belarus is always ready to offer (Minsk) as a negotiations venue."
A senior Ukranian source had earlier told AFP that there was still a possibility that a meeting in Minsk could be arranged for Friday if more preliminary consultations were held.