The United States is "concerned" by reports of North Korean soldiers fighting for Russia in Ukraine, according to a White House spokesperson on Tuesday.
Ukrainian President Volodymyr Zelenskiy this week accused North Korea of transferring personnel to Russia's armed forces, saying his intelligence agencies had briefed him on "the actual involvement of North Korea in the war" in Ukraine.
The Kremlin has dismissed the allegation as "fake news."
In a statement, White House National Security Council spokesperson Sean Savett said the involvement of North Korean troops in Ukraine, if true, would mark a significant increase in the North Korea-Russia defense relationship.
"Such a move would also indicate a new level of desperation for Russia as it continues to suffer significant casualties on the battlefield in its brutal war against Ukraine," Savett said.
Washington says North Korea has supplied Russia with ballistic missiles and ammunition. Moscow and Pyongyang have denied arms transfers but have vowed to boost military ties, possibly including joint drills.