In her address to the Permanent Council, Byrnes reminded that Ukraine had "called for an immediate period of silence to allow repairs to critical infrastructure" in Avdiyivka, adding that it is "also attempting to convene an emergency meeting of the Trilateral Contact Group and has urged the Special Monitoring Mission to step up patrols in the area."

"Nonetheless, combined Russian-separatist forces have insisted they will continue to fight until Ukrainian forces retreat," Byrnes said. "Russia and the separatists initiated the violence in Avdiivka."  

Read alsoUNSC concerned about Donbas, to meet on Feb 2 amid Ukraine's presidency"We call on Russia to stop the violence, honor the ceasefire, withdraw heavy weapons, and end attempts to seize new territory beyond the line of contact," said the chief of the U.S. Mission to the OSCE.

Noting that the temperatures have dropped far below freezing in Ukraine, Byrnes emphasized that "without water, electricity, or heat, the lives of thousands of people are at stake".  

Read alsoU.S. concerned with spike in violence near Avdiyivka, DonbasShe urged the combined Russian-separatist forces to halt their attack on Avdiyivka: "They must stop the violence and allow repairs to critical infrastructure. Most of all, Russia and the separatists must demonstrate their willingness to fully abide by the ceasefire, a primary component of the Minsk agreements that they have so often broken."