He said this in an interview with CBS News.
Zelenskyy stressed that Ukraine needs the help of its partners because it is expected that Russia may launch a new major offensive in the country in late May or June.
"And before that, we not only need to prepare, we not only need to stabilize the situation, because the partners are sometimes really happy that we have stabilized the situation," Zelenskyy said, emphasizing that Ukraine needs help now.
The President said that Russia has an advantage in the "artillery war of attrition" due to the long-range firepower.
"In Bakhmut and Avdivka and Lysychansk and Soledar and so on, it was really hard to fight the adversary, whose artillery shell can fire 20-plus kilometers, and [our] artillery shell is 20-minus," he added.
Zelenskyy also noted that usually when Russians attack and destroy Ukrainian villages, they try to occupy them.
"We don't know what will be tomorrow. That's why we have to prepare," the Ukrainian president said.
On February 25, Ukrainian President Volodymyr Zelenskyy said that Russia would be preparing for an offensive in late May or early summer. Ukraine will prepare to fight back.