Ukraine had hoped to start its highly anticipated counteroffensive earlier in the spring, but held off because it lacked the necessary weapons, Ukrainian President Volodymyr Zelenskyy said.

“We did have plans to start it in spring. But we didn’t, because, frankly, we had not enough munitions and armaments and not enough brigades properly trained in these weapons, still, more, that the training missions were held outside Ukraine,” Zelenskyy said during an interview that aired Sunday on CNN’s “Fareed Zakaria GPS.”

Because the counteroffensive began later, Zelenskyy said, speaking through a translator, “it provided Russia with time to mine all our lands and build several lines of defense. And, definitely, they had even more time than they needed. Because of that, they built more of those lines. And, really, they had a lot of mines in our fields.”

“Because of that, a slower pace of our counteroffensive actions. We didn’t want to lose our people, our personnel. And our servicemen didn’t want to lose equipment because of that,” he told Zakaria.

In May, Zelenskyy whipped around Europe on a three-day trip that included stops in Italy, the Vatican, Germany, France and the United Kingdom, pressing allies to send more weapons as his military geared up for the planned counteroffensive. But the promise of F-16 fighter jets — which Zelenskyy had repeatedly pressed the U.S. and other allies for — didn’t come until days later. Those jets are set to arrive in Ukraine toward the end of the year.

Zelenskyy has acknowledged that progress in pushing back Russian forces has been “slower than desired.” But during a virtual appearance at the Aspen Security Forum last week, he told international leaders that his military is “approaching [the] moment when actions can gain pace.”

On Sunday, a Russian missile barrage in Ukraine’s southern port city, Odesa, left at least one dead and damaged a cathedral in the city’s center.