Ukrainian President Volodymyr Zelensky warned Monday that North Korea is gaining battlefield experience and improving its military capabilities through its support for Russia.

SEOUL, Aug. 11 (UPI) -- Ukrainian President Volodymyr Zelensky warned Monday that North Korea is gaining battlefield experience and improving its military capabilities through its support for Russia, posing a growing threat to U.S. allies and other countries in the Asia-Pacific region.

In an address from the presidential office in Kyiv, Zelensky said North Korea was preparing to send a new contingent of troops to Russia and had supplied Moscow with additional ballistic missiles.

"This is the first time in Russia's history that they no longer have a secure strategic rear," Zelensky said. "For the first time, they cannot wage war without reinforcements from North Korea."

North Korea has sent munitions and roughly 15,000 troops to support Russian forces in the Kursk region, according to South Korea's National Intelligence Service, which estimates that about 2,000 of the deployed troops have been killed.

On Sunday, Zelensky said North Korea was preparing to deploy an additional 30,000 to 50,000 personnel to Russia and called for closer cooperation between Seoul and Kyiv.

"We would very much like to receive support from South Korea in an area where we have a shortage," he wrote on X. "That is air defense systems. They have a legal restriction under their Constitution. We would like to have this cooperation and are counting on it. Our diplomats are in contact."

Seoul has maintained a policy of providing humanitarian and nonlethal assistance to Ukraine while declining to directly supply lethal weapons.

Zelensky said Monday that the battlefield experience North Korea was gaining in Russia posed a mounting threat to countries in the Asia-Pacific region.

"The more [North Korean] missiles and soldiers are used, the more they correct their shortcomings and blind spots, the greater the danger will later be for Japan, the Republic of Korea, the Philippines, and other countries in the region," he said.

Zelensky added that international support for Ukraine could help deter Pyongyang from using the conflict to test and improve its military capabilities.

"We are also, in fact, speaking about taking away North Korea's appetite and any interest in coming here -- to our land and into our skies -- with its weapons in order to learn how to wage war," he said.

The United States and South Korea are incorporating the threat posed by North Korea's battlefield experience into their upcoming major summer joint military exercise, officials said Monday.

"DPRK soldiers have deployed and fought in Ukraine and they've taken those lessons they learned there and brought them back to North Korea," U.S. Forces Korea spokesman Col. Ryan Donald said at a press briefing. "That changes the DPRK capability and our training accounts for that threat."

The Democratic People's Republic of Korea is the official name of North Korea.

Seoul's Foreign Ministry on Tuesday called for an immediate halt to North Korea-Russia military cooperation but declined to confirm Zelensky's estimate of the size of a potential new deployment.

"Our government considers military cooperation between North Korea and Russia to be a matter directly linked to our security and an act that violates U.N. Security Council resolutions," ministry spokesman Park Doo-soon said.

Park also declined to comment on diplomatic discussions over potential South Korean defense assistance to Ukraine, saying Seoul's provision of military equipment to other countries is conducted in accordance with domestic laws and policies.

"We have provided support to Ukraine in various fields, including energy, infrastructure, health, medical care, and education, and we plan to continue reviewing measures for the restoration of peace and reconstruction in Ukraine," he said.