"This easing alone by the United States could provide Russia with about $US10 billion ($A14 billion) for the war," Zelenskiy told a news conference with French President Emmanuel Macron during a visit to Paris.
"This certainly does not help peace.
"I believe that lifting sanctions will, in any case, lead to a strengthening of Russia's position. It spends the money from energy sales on weapons, and all of this is then used against us.
"Therefore, ultimately lifting sanctions only so that more drones will later be flying at you is, in my opinion, not the right decision."
The US Treasury Department announced Thursday a 30-day waiver on Russian oil sanctions. The step aims to free up Russian cargoes stranded at sea and ease supply shortages caused by the Iran war.
Analysts say that spiraling oil prices due to Persian Gulf production blockages are benefiting the Russian economy. Moscow relies heavily on oil revenue to finance its invasion, and sanctions were a growing handicap.
US-mediated talks between Moscow and Kyiv that seek to stop Europe's biggest conflict since World War II are on hold due to the Iran war, though they could resume next week, according to Zelenskiy.
Macron noted that broad sanctions on Russia still stand despite the temporary US waiver.
US waivers announced in recent days are "limited" and "taken on an exceptional basis," Macron said.
"It does not broadly or permanently roll back the sanctions that they themselves decided to apply," he added.
German Chancellor Friedrich Merz adopted a more critical stance. He said Friday that a meeting earlier this week of heads of state and government from the Group of Seven industrialised democracies discussed with US President Donald Trump the issue of Russian oil and liquefied natural gas supplies.
"Six members of the G7 expressed a very clear view that this (waiving of Russia sanctions) is not the right signal to send," Merz said during a visit to Norway.
"We learned this morning that the US government has apparently decided otherwise. Once again, we believe this is the wrong decision."
Merz added: "There is currently a price problem, but not a supply problem. And in that regard, I would like to know what additional motives led the US government to make this decision."
Ukraine has become one of the world's leading producers of drone interceptors, and Kyiv is offering its expertise to the United States and its Gulf partners for the war in the Middle East, hoping to receive in return the high-end weaponry it can't manufacture at home.
But Trump spurned Ukraine's offer of assistance to the US in comments aired Friday.
"No, we don't need their help on drone defence," Trump told Fox News Radio.
Zelenskiy had said on Thursday that Ukraine is awaiting White House approval for an agreement on producing battle-tested drones.
In Paris, he said Kyiv had received a request for drone combat assistance from Washington. The cause of the discrepancy between the leaders' comments was not immediately clear.
Zelenskiy said that Ukraine has received requests from six countries for help with drones. It has already sent expert teams to three countries, he said, without naming them.
Zelenskiy noted that providing interceptors was not enough to help fight drone attacks. The Ukrainian military has expertise in deploying the systems, he said.
"There must be proper, systematic work with radars and with the entire air defence system," Zelenskiy said.
"Ukraine is ready to share this experience for the sake of the security of those partners who are helping us."
