Senior U.S. and Ukrainian officials are set to meet for talks on the war in Saudi Arabia on Tuesday. Zelenskyy will also visit Monday for talks with Crown Prince Mohammed bin Salman.
For the U.S., Witkoff has said he wants to discuss an "initial ceasefire" with Russia and a "framework" for a longer agreement.
Zelenskyy said Ukraine would be represented by officials including Foreign Minister Andriy Sybiga and Defense Minister Rustem Umerov.
In his evening address, he told Ukrainians he was "confident that the meeting will be productive."
Zelenskyy also urged allies to "increase sanctions against Russia" after heavy overnight bombardment in the east and northeast.
A Russian barrage hit the centre of Dobropillia in the eastern Donetsk region late Friday, killing 11 people and wounding 40, according to the emergency services.