US officials on Wednesday said they have evidence that North Korea has sent about 3,000 troops to Russia to undergo military training.
Defence Secretary Lloyd Austin told reporters in Rome that it was unknown if those troops would be sent to fight on Russia's side in the war in Ukraine.
“What exactly they’re doing is left to be seen. But yes, there is evidence that there are DPRK troops in Russia,” he said, using the abbreviation for the Democratic People’s Republic of Korea.
“If they're co-belligerents, if their intention is to participate in this war on Russia's behalf, that is a very, very serious issue.”
National Security Council spokesman John Kirby said the North Korean soldiers had travelled by ship from the Wonsan area to the eastern Russian city of Vladivostok between early to mid-October. They were then taken to military training sites in eastern Russia, he said.
“If North Korean soldiers do enter into combat, this development will demonstrate Russia's growing desperation in its war against Ukraine,” Mr Kirby told reporters.
In June, North Korea's leader Kim Jong-un and Russian President Vladimir Putin signed a defence treaty.
The two US officials said the latest development would not only affect the nearly three-year-old war on Ukraine, it would also affect Europe and the Indo-Pacific region.
Moscow and Pyongyang have both denied any deployments, although North Korea has previously provided munitions to Russia.