White House national security spokesman John Kirby said Friday that top national security advisers from the United States, Japan and South Korea met with “serious concerns” about North Korea’s deployment of troops for potential use alongside Russia on the battlefield against Ukraine. he said.

Kirby said the three countries’ national security advisers “call on Russia and North Korea to halt these actions that serve to expand the security consequences of Russia’s brutal and illegal war beyond Europe and into the Indo-Pacific.”

“It’s possible there are more than 3,000 troops from North Korea sent to Russia for equipment and training,” Kirby said during a call with reporters.

Kirby said the U.S. government does not have definitive intelligence assessments of where the troops are going, but believes it is certainly possible and “even likely” that some of the North Korean troops will be deployed to Russia’s Kursk region. Ukraine has retained some territory since seizing it in August. But he warned that he did not know in what capacity and for what purpose North Korean troops would be deployed.

A senior official in the Ukrainian presidential office told The Associated Press on Friday that Zelenskyy canceled a planned visit by U.N. Secretary-General Antonio Guterres to Kiev.

The official, who requested anonymity because he is not authorized to speak publicly on the subject, said that the visit will take place this week after the summit in the BRICS emerging economies bloc in Kazan, Russia, which Guterres also attended.

A photo of Guterres shaking hands with Russian President Vladimir Putin at the summit caused great reaction in Ukraine.

In a post on Telegram, Zelenskyy said that Ukrainian intelligence had determined that between Sunday and Monday “the first North Korean army will be used by Russia in war zones.”

He said on Telegram that the deployment was “clearly an escalating move by Russia.” North Korea did not provide further details, including where its troops might be sent.

Russia is waging a fierce summer campaign on Ukraine’s eastern front, slowly forcing Kiev to surrender. But Russia has struggled to dislodge Ukrainian forces from the Kursk border region following an attack almost three months ago.

According to the Main Intelligence Directorate of Ukraine, known by its acronym GUR, North Korean units were detected in Kursk on Wednesday.

GUR said late Thursday that soldiers had been training for several weeks at bases in eastern Russia and were equipped with clothing for the coming winter.

The number of North Korean soldiers Pyongyang sent to Russia is estimated to be around 12,000, including 500 officers and three generals.

GUR provided no evidence of its allegations.

Dutch Defense Minister Ruben Brekelmans said on social platform X on Friday that intelligence reports indicate that North Korean troops “will probably be deployed first in Kursk.”

The deployment of North Korean forces under a military agreement signed between Moscow and Pyongyang adds a new dimension to the conflict, which is Europe’s largest war since World War II and has claimed tens of thousands of lives, including many civilians, on both sides.

The United States said on Wednesday that 3,000 North Korean soldiers were deployed to Russia and trained in various locations, saying this move was very serious.

Zelenskyy said a week ago that his government had intelligence information that 10,000 soldiers from North Korea were preparing to join Russian forces fighting against his country. He said a third country involved in hostilities would turn the conflict into a “world war”.

North Korea was already supplying munitions to Russia under a defense pact, but fielding troops could seriously complicate a war that has inflamed international politics with most Western countries backing Kiev.

Meanwhile, Putin sought support among the BRICS countries.

He neither confirmed nor denied that North Korean troops were in Russia.

Mike Corder from The Hague and Josh Boak from Washington contributed.