Ukrainian President Volodymyr Zelenskyy said Friday that Russia is expected to deploy North Korean soldiers to combat as early as Sunday.

In a statement posted to his official X social media account, Zelenskyy said the prediction is based on military intelligence he received in a Friday briefing from armed forces Commander-in-Chief Oleksandr Syrskyi.

Zelenskyy called the move a “clear escalation by Russia,” adding that “the world can clearly see Russia’s true intentions: to continue the war.”

Calling for a “principled and strong response” from global leaders, Zelenskyy said, “North Korea’s actual involvement in combat should not be met with indifference or uncertain commentary, but with tangible pressure on both Moscow and Pyongyang, to uphold the U.N. Charter and to hold them accountable for this escalation.”

Responding Thursday to a Ukraine intelligence report that the North Korean troops were in Russia’s Kursk region, Russian President Vladimir Putin said it was up to Moscow to decide how they might be deployed, including possibly sending them to fight on the front lines against Ukraine. He did not deny a U.S. claim that North Korea has dispatched some 3,000 troops to fight alongside Russian forces.

On Friday, North Korean state broadcaster KCNA carried a statement by Vice Foreign Minister Kim Jong Gyu, who would not comment directly on reports of the deployment, but said if there were such a thing, “I think it will be an act conforming with the regulations of international law."

Ukraine has argued North Korean participation in the war violates international law; U.S. officials earlier this week called such a deployment a major escalation. But Putin argued the West had escalated the war in Ukraine by sending NATO officers and instructors to help Kyiv defend itself against Russian aggression.

Meanwhile, in an interview with Russian television Friday, Putin spoke about possible cease-fire negotiations with Ukraine, saying Russia was ready to seek compromises. He said Turkey had presented a number of peace initiatives to both Russia and Ukraine, which he claimed Ukraine has rejected.

Regarding possible compromises, Putin said: “Any outcome must be in Russia's favor. ... This outcome should be based upon the realities which are taking shape on the battlefield. Without any doubt, we are not going to make any concessions. There will be no exchange [of territory], whatsoever."

Putin blamed Ukraine for what he described as “irrational behavior” in negotiations, saying, “It is not possible to build any plans on this basis.”

Bio lab construction

In an exclusive report Friday, The Washington Post said satellite images from the past two years have shown substantial construction at a site-restricted military facility northeast of Moscow that was once a major research center for biological weapons.

The report said the site has a history of experiments that included viruses that cause smallpox, Ebola and hemorrhagic fevers.

The satellite imagery of the Russian site, called Sergiev Posad-6, shows construction vehicles renovating the Soviet-era laboratory and breaking ground on 10 new buildings, totaling more than 250,000 square feet, with several of them bearing hallmarks of biological labs designed to handle extremely dangerous pathogens.

The report said there has been no sign such weapons are being used in the Ukraine conflict, but the construction is being closely watched by U.S. intelligence agencies and bioweapons experts.

Ukraine’s Kyiv Independent reported Friday the apparent deployment of North Korean troops could be at least in part a result of Russia’s losses on the battlefield.

In a report on its Facebook social media account, the Ukraine General Staff of the armed forces reported Russia has lost 685,910 troops since the beginning of its full-scale invasion of Ukraine on Feb. 24, 2022. This includes, the general staff report said, 1,630 casualties over a 24-hour period ending Friday.

Ukraine has closely guarded its battlefield troop casualties, even from Western allies, but a U.S. official in September estimated Ukraine has likely seen an estimated 57,500 troops killed and 250,000 wounded, according to a report by The New York Times.

Battlefield casualties are difficult to verify, and Russia has made claims that Ukrainian casualties are much higher than those indicated by Ukrainian and U.S. estimates.

Some information for this report was provided by The Associated Press, Reuters and Agence France-Presse.