Ukrainian officials and pro-Russian rebels will not be meeting in Belarus' capital Minsk for a round of peace talks scheduled for Friday.
Belarussian officials on Friday announced the breakdown of the negotiations but did not give a reason. It is not clear if the talks will resume at a later date.
Talks between Ukrainian government negotiators and their pro-Russian separatist counterparts have failed to produce any breakthrough to end the eight-month conflict in eastern Ukraine.
Separatist leaders were quoted as saying Thursday that the only tangible result of the talks in Belarus this week was an agreement on the terms of a prisoner exchange of about 400 fighters.
Peace efforts have also involved Russian officials and mediators from the Organization for Security and Cooperation in Europe.