Kyrylo Budanov, the head of the Office of Ukraine's President, addressed the nation and said Russia was now willing to accept security guarantees for Ukraine, as they have "no alternative."

"On security guarantees, the Russian side said directly they would accept the guarantees the United States is proposing to Ukraine—they have no alternative," he said.

Budanov said such guarantees are essential to achieving peace.

"I think security guarantees will be activated alongside the end of the war, if we reach that point," Budanov said.

Ukraine's President Volodymyr Zelensky has said President Trump wants to sign an agreement for security guarantees and to bring an end to the war at a high-profile ceremony.

Zelensky has maintained firmly that guarantees must be achieved by Congress, making them binding, before he signs for peace.

He has also said a direct meeting with Vladimir Putin will be needed to resolve the most difficult issues.

At the beginning of last month, Zelensky said President Trump has set a deadline of June this year to bring the war in Ukraine to an end.

"The Americans are proposing the parties end the war by the beginning of this summer," Zelenskyy said.

Washington wants "a clear schedule of all events," he added, and will apply pressure "precisely according to this schedule" if progress falters.

Zelensky went on to say that US officials were prepared to "do everything" to end the war; although he did not say exactly what that means.

Intense fighting continues in the eastern Donbas region of Ukraine, which Moscow wants to retain full control of after the war.