Ukraine's President Volodymyr Zelenskyy told CBS News in an exclusive interview that his government has evidence that Russia is abducting Ukrainian children and training them to fight against fellow Ukrainians.

It is an allegation that may constitute a war crime, according to the International Criminal Court. This is the first time that Zelenskyy has publicly made this accusation, which goes beyond the documented evidence that Russia has a state-sponsored program of taking Ukrainian children to camps for reeducation or "Russification."

"When these children grow up and they push these boys to the battlefield," Zelenskyy said.

Zelenskyy said "yes have evidence of it," but he did not detail what the evidence his government has. 

"Yes, and they taught these children to hate their native country, to hate native people," Zelenskyy said. "And Ukrainians, can you imagine, such young Ukrainians, young boys, come to the battlefield and kill Ukrainians." 

The International Criminal Court issued a warrant for Vladimir Putin's arrest in 2023 due to what it referred to as a program of "unlawful deportation of population (children)." The Kremlin called it a humanitarian effort to care for war orphans, and has broadcast images of Putin and the ICC-indicted program head Maria Lvova-Belova embracing some of the kids.

In an exclusive interview with Margaret Brennan that aired Sunday on "Face the Nation," Zelenskyy emphasized that Russia has long been treating children essentially as combatants, and offering to trade the children for soldiers captured on the battlefield. International humanitarian law provides broad protections for children as non-combatants. 

"It's important to get back our warriors, war prisoners, but we can't exchange them [for] the children," he said. 

"Can you imagine, how we can exchange our children?" he said. "We can't. First of all, it's out of the law. We can't exchange civilians." 

The previously U.S. government-backed Humanitarian Research Lab at the Yale School of Public Health, which investigates war crimes, concluded with high confidence in a report in March that Gazprom and Rosneft, both Russian state-owned oil and gas companies, helped underwrite the reeducation of more than 2,000 Ukrainian children. 

The report also argued that the Trump administration's decision to issue temporary sanctions relief on Russian oil at sea has provided a windfall for both companies. 

"Gazprom and Rosneft are the first known Russian Federation-affiliated corporate entities related to child deportation that are currently making money from U.S. consumer spending at the time of this publication," the Yale report said.

The U.S. first issued a sanctions waiver in March in an attempt to put supply on the market to offset skyrocketing prices because of the war with Iran. The waiver has been extended twice and, according to Treasury Secretary Scott Bessent, the extension came at the request of countries in Asia hungry for oil supplies.

Brennan asked Zelenskyy whether the temporarily lifting of U.S. sanctions off some Russian oil sales is inadvertently fueling that abduction program.

"Lifting sanctions is a help for the soldiers of Russia," he said. 

He said his government has spoken with lawmakers about imposing stricter sanctions on Russia in retaliation for the alleged child abduction scheme. 

"I hope that Congress will find the possibility again to put sanctions on Russians, because of the children," he said. "We spoke with congressmen, we spoke so many times about it. I hope that they will make this step."

Zelenskyy also told CBS that Ukraine has documented the abduction of at least 20,000 Ukrainian children, and wants help tracking down what he suspects are even higher numbers.