Ukraine has relied on US intelligence to spot the fast-moving ballistic missiles that Russia has fired in waves at its cities.
US President Donald Trump had said that Washington was still sharing intelligence, although Ukrainian officials said some Russian strikes had occurred without warning.
Speaking to NBC's Meet the Press, Zelenskiy said intelligence-sharing had been interrupted but later "de-blocked".
"We are very thankful for this," he said.
"Now it works."
But Zelenskiy said other US actions, such as signing a deal to import Russian diesel and waiving sanctions on Russia that had been slated to take effect this week, will hurt Ukraine.
"If the United States will officially take the side of Russia, of course if these two countries will be together, of course we will not prevail and we will not be able to stand," he said.
Over the past week, a widening rift between Trump and Zelenskiy has sparked concerns that their tumultuous relationship could lead to even worse outcomes for Kyiv.
Zelenskiy told NBC he hopes Trump will remain an ally of Ukraine.
"We want to trust him, and I hope that he will change his decisions," Zelenskiy said.
"Because I think that it's all mistakes and it will not help us. And it will not help United States."
In a Truth Social post on Sunday, Trump wrote that his decision-making was aimed at avoiding anything "that will drive, foolishly, Russia away from the bargaining table".
Ukraine gets US help that Russia does not receive, US Treasury Secretary Scott Bessent told NBC, citing intelligence-sharing and the provision of US munitions to other countries for resale to Ukraine.
But Bessent, speaking with Meet the Press after it aired Zelenskiy's interview, did not directly answer when asked multiple times whether the US views Ukraine as an ally.
"Zelenskiy presents a false binary this morning that Ukraine must win," Bessent said.
"The war must end, and that will be with some kind of a negotiated settlement."
Meanwhile, a Russian air strike killed one person and injured two in Ukraine's capital of Kyiv overnight, Mayor Vitali Klitschko said on Telegram early on Monday.
A medical facility and a non-residential building were damaged in the attack, he said.
