"June and July this year may determine a lot," President Volodymyr Zelensky said.

Ukrainas president Volodymyr Zelenskyj ansluter till de nordiska och baltiska ledarna under ett toppmöte i Estland på tisdagen.

Ukrainian President Volodymyr Zelenskyy is in Estonia to attend a summit of Nordic and Baltic leaders. He is expected to meet with Estonian President Alar Karis.