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

As Ukrainian forces mount a new offensive in Russia’s Kursk region, U.S. Secretary of State Antony Blinken on Monday said that success in this region would improve Kyiv’s bargaining position in any future ceasefire negotiations.

Russian forces continue to make costly but consistent gains in the Donetsk region in eastern Ukraine. They are steadily grinding down a pocket of resistance around the town of Kurakhove and are also fighting to envelop the larger nearby city of Pokrovsk, Ukrainian soldiers and officials said.