The United Nations and the International Committee of the Red Cross have directed Russian President Vladimir Putin to remove his "mountain of corpses," Ukrainian President Volodymyr Zelenskyy said Saturday. 

"They abandoned their military," Zelenskyy said in an interview with a Ukrainian news outlet. "They were dying, but they didn't care. Recently I was told that they are only now thinking about taking the corpses. 

"When the war started…they used to pretend that there were no corpses," he continued. "The UN and the Red Cross said – take these bags away. Mountains of corpses of their military."

Russian armored vehicle burns in fight

A Russian Armoured personnel carrier (APC) burns next to an unidentified soldier's body during a fight with the Ukrainian armed forces in Kharkiv. (Photo by SERGEY BOBOK/AFP via Getty Images)

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Moscow has long relied on its propaganda machine to fuel support for its conflict in Ukraine and Putin has refused to declare open war on Kyiv, instead calling it a "special military operation."

Reports surfaced early in the invasion that Russia was potentially relying on a "mobile crematorium" to dispose of dead soldiers to help cover the evidence of mounting causalities. 

The Pentagon has assessed that Russia is behind schedule in eastern Ukraine, where it intends to gain "full control."

But press secretary John Kirby said Friday that the U.S. has assessed that Russian forces are still making "incremental gains" in the Donbas and a senior U.S. defense official told reporters this week the U.S. believes Moscow is making some headway in the Black Sea as well.

"The Russians are still well behind where we believe they wanted to be when they started this revitalized effort in the eastern part of the country," Kirby said from the Pentagon. "And while they have made, and we have been very honest about this, they have made some incremental progress in the Donbas. It is incremental, it is slow, it's uneven, and the Ukrainians continue to push back."

Volodymyr Zelenskyy

President of Ukraine Volodymyr Zelenskyy and his wife Olena Zelenska attend the funeral of Leonid Kravchuk, independent Ukraine's first president, at the International Convention Center Ukrainian House, in Kyiv, Ukraine, Tuesday, May 17, 2022. Kravchuk led Ukraine to independence amid the collapse of the Soviet Union and served as its first president. He died on May 10 at the age of 88.  (AP Photo/Evgeniy Maloletka)

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Zelenskyy said Ukrainians are fighting to protect their independence and championed that 700,000 Ukrainians are fighting against Russian forces across the war-torn nation. 

The Ukrainian president said he signed a decree in early 2022 to add 100,000 additional troops to its fighting force by next year, but warned he is not sure that this will be enough to take on the entire might of Russia.

Western defense officials have argued Russia does not appear to have properly planned for its major offensive against Ukraine, and Zelenskyy said Saturday his nation had been bracing for an attack since September 2021 as Russia started to amass troops along its southern border.

But Zelenskyy said that Ukraine is fighting more than just Russia and has Belarus to contend with as it has backed Putin's deadly campaign.

soldiers Ukraine flag

Soldiers place the Ukrainian flag on the coffin of 41-year-old soldier Simakov Oleksandr, during his funeral ceremony, after he was killed in action, at the Lychakiv cemetery, in Lviv, western Ukraine, Monday, April 4, 2022.  (AP)

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Zelenskyy said he could not predict when the war with Russia would end, but said Ukrainians have already psychologically "broken" Russia’s forces by prolonging a fight Putin apparently believed would last a matter of weeks.

"We have to look at the cost of this war," he said. "We broke the back of one of the world's strongest armies. We have already done it. Psychologically we have done it. 

"They will not stand on their feet for the next few years," he added.