NATO formally invited Finland and Sweden to join the military alliance.
Turkey agreed on Tuesday to drop its objections to their membership offers, removing a major hurdle for them to join NATO.
Alliance leaders are expected to announce a significant buildup of forces along its eastern edge, with US President Biden to unveil an enhanced US force posture in Europe.
Russian forces are making some progress in their efforts to encircle the city of Lysychansk and may be able to trap some Ukrainian forces.
Russian-backed authorities in the occupied Kherson region of southern Ukraine say they are preparing for a referendum to join the Russian Federation.