It comes as Ukraine's president says only the US can provide security guarantees leading to an end to the war.

Ukrainian forces on Sunday launched a new offensive inside Russia's western Kursk border region, going on the attack with substantial forces.

Ukraine launched a new offensive in Russia's Kursk region Sunday, Moscow and Kyiv said. Ukrainian forces had captured about 500 square miles of the western Russian province in a surprise incursion in August, but Russian and North Korean troops are believed to have retaken 40-50% of that area.