The Kremlin said it reserves the right to use nuclear weapons if it faces aggression by Western countries. Overnight, Moscow attacked Kyiv, killing at least eight people.

Imposing a deadline on a negotiation for a deal you desperately want is a risky tactic if your only move is to walk away from a deal you desperately want.

Many of the elements of the U.S. proposal would be politically damaging to Zelensky, creating an opening Moscow could exploit, say analysts and officials.