Why it matters: The U.S. and Ukraine both endorsed an unconditional 30-day ceasefire on Tuesday that calls for all air and artillery strikes to stop and fighting to cease all along the front lines. Putin raised doubts about that idea, and said any ceasefire should also be part of a process that addresses the "root causes of this crisis."

As momentum builds for a ceasefire with Russia, Ukraine has all but lost a valuable bargaining chip. The Ukrainian army stunned Russia in August by attacking across the border and taking control of an estimated 1,