President Volodymyr Zelenskiy criticized what he termed his allies’ “zero” response to Russia’s deployment of North Korean troops in the Ukraine conflict, stating on Thursday that a weak reaction could embolden Vladimir Putin to increase the troop presence.

In an interview with South Korea’s KBS television, Zelenskiy expressed his belief that Moscow is seeking to arrange for North Korea to send engineering troops and a significant number of civilians to assist at Russian military facilities.

“Putin is gauging the West’s reaction… I believe that based on the current responses, Putin will decide to expand the contingent… The current reaction is non-existent, it’s zero,” Zelenskiy remarked.

He had been warning about North Korean involvement since October 13. While Western allies have acknowledged the deployment as a major escalation, they have yet to announce any retaliatory actions or indicate preparations for such measures.

South Korea has offered to assist with intelligence and is exploring the possibility of sending a team of military monitors to Ukraine, according to South Korean officials.

In prepared remarks to the U.N. Security Council on Wednesday, Ukraine’s delegation identified three North Korean generals who they claim are accompanying thousands of troops from the Korean People’s Army sent to Russia to support its military efforts in Ukraine.

Russia has not denied the involvement of North Korean forces in the conflict. Initially, North Korea denied any involvement but has since justified the troop deployment as consistent with international law.

Deputy U.S. Ambassador to the United Nations, Robert Wood, informed the Security Council on Thursday that the U.S. has received intelligence indicating that “right now” there are 8,000 North Korean troops in Russia’s southern Kursk region, which borders northeastern Ukraine.

During the interview, Zelenskiy expressed surprise at China’s “silence” regarding the troop deployment, noting that Ukraine had “clear information” confirming that Russia had communicated the deployment of North Koreans to the West through intelligence channels.

“The Russian Federation discussed this with the West and confirmed that there are indeed North Korean military personnel who will be fighting against Ukraine,” he stated.

Zelenskiy’s direct comments reflect growing frustration in Ukraine over the level of Western support at a crucial juncture in the conflict with Russia, especially with the U.S. presidential election approaching on Tuesday.

Russian forces have been making gradual advances in eastern Ukraine for months, while Ukraine’s outnumbered and outgunned troops have been struggling to hold back the offensive.