Officials in Belarus say plans for a key round of peace talks between Ukraine and pro-Russian rebels have been canceled.
A round of negotiations between representatives of Ukraine, Russia, pro-Russian rebels and the OSCE had been tentatively scheduled to be held on December 26 in Minsk.
Kyiv had hoped the meeting would lead to the signing of a final peace deal on ending fighting in eastern Ukraine.
A previous round of talks on December 24, however, ended with little progress beyond an agreement on exchanging prisoners of war.
Ukraine's security service says Kyiv is set to swap 225 rebels for 125 Ukrainian servicemen.
A spokesman for the rebels said the swap would take place by December 30.
Markiyan Lubkyvsky, a spokesman for Ukraine's SBU state security service, refused to confirm the date, saying only that the swap would take place "soon."