MOSCOW (AP) — Ukraine's military has postponed a second stage of a weapons pullback in the country's conflict-ridden east, drawing criticism from the Kremlin's envoy to a group trying to help end the fighting.

The military said the pullback near the town of Petrovske, which was tentatively set for Monday, could not be conducted because of recent cease-fire violations.

Ukrainian forces and Russia-backed separatists have fought since 2014 in a war that has killed more than 13,000 people. A Ukrainian heavy weapons pullback elsewhere in the east last week raised hopes that a stumbling peace process was advancing.

Boris Gryzlov, Russia's representative to the Contact Group of Ukraine, Russia and the OSCE, says "we are once again convinced that the main reason for the stalling of the .... process is the position of Kyiv."