Pentagon spokesperson Sabrina Singh told reporters Monday that some of the North Korean soldiers have already moved closer to Ukraine and were believed to be heading for the Kursk border region, where Russia has been struggling to push back a Ukrainian incursion.

The agency said space-based reconnaissance is an area where North Korea is likely receiving Russian help.

It said North Korea may be acquiring advanced components from Russia as it prepares to launch another military reconnaissance satellite following a failed attempt in May, said Park Sun-won, another lawmaker who attended the hearing.

North Korea first placed a spy satellite in orbit last November.

Its leader Kim Jong Un has described those assets as crucial for monitoring South Korean and U.S. military activities and enhancing the threat of his nuclear-capable missiles.

South Korean President Yoon Suk Yeol in telephone calls with European Union Commission President Ursula von der Leyen and NATO Secretary-General Mark Rutte on Monday shared South Korean intelligence assessments that North Korean troops could be deployed to battlefronts “more quickly than anticipated.”

He called for closer coordination with European governments aimed at “monitoring and blocking “illegal exchanges between Pyongyang and Moscow, Yoon’s office said in a statement.

After initially denying the claims about North Korean troop deployments, Pyongyang and Moscow have adopted a vaguer stance, asserting that their military cooperation conforms with international law without directly admitting the presence of North Korean forces in Russia.

North Korea has also been accused of providing millions of artillery shells and other military equipment to Russia to fuel its war in Ukraine.

The United States and its partners have described Russia’s procurement of North Korean personnel and supplies as a violation of U.N. Security Council resolutions, and raised suspicions that Moscow is helping Pyongyang to evade sanctions and unlawfully finance its weapons program.

Russia, along with China, has blocked U.S.-led efforts at the Security Council to tighten sanctions on North Korea over its recent missile testing activities.

Russia also vetoed a U.N. resolution to extend the mandate of a panel of monitors in March in a move that effectively abolished oversight by U.N. experts of Security Council sanctions against North Korea.

It prompted Western accusations that Moscow was acting to shield its arms purchases from Pyongyang.

“The illegal military collusion between Russia and North Korea poses a significant security threat to the international community and a serious matter that could potentially harm our security. We must thoroughly examine all possibilities and prepare countermeasures,” Yoon said in a Cabinet meeting in Seoul on Tuesday.

Yoon last week raised the possibility of supplying Ukraine with weapons while saying Seoul is preparing countermeasures that could be rolled out in stages depending on the degree of military cooperation between Pyongyang and Moscow.

South Korea, a growing arms exporter, has provided humanitarian aid and other non-lethal support to Ukraine and joined U.S.-led economic sanctions against Moscow.

It has so far resisted calls by Kyiv and NATO to directly supply Ukraine with weapons, citing a longstanding policy of not providing arms to countries engaged in active conflict.