Washington: The United States is "concerned" by reports of North Korean soldiers fighting for Russia in Ukraine, a White House spokesperson said on Tuesday.
Ukrainian President Volodymyr Zelenskyy 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."
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 in a statement.
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.
The US Army's Indo-Pacific commander, General Charles Flynn, told an event in Washington that North Korean personnel being involved in the conflict would allow Pyongyang to get real-time feedback on its weapons, something that had not been possible in the past.
"That's different because they are providing capabilities and – open source reporting – there's manpower that is also over there," he said at the Center for a New American Security.
"That kind of feedback from a real battlefield to North Korea to be able to make adjustments to their weapons, their ammunition, their capabilities, and even their people – to me, is very concerning," he said.
Russian President Vladimir Putin signed a treaty with North Korean leader Kim Jong Un when he visited Pyongyang in June, and said it included a mutual assistance clause under which each side agreed to help the other repel external aggression.