North Korean troops deployed to fight for Russia against Ukraine are "fair game," U.S. National Security Council spokesperson John Kirby said on Oct. 23.
Earlier in the day, the U.S. made its first public confirmation that it had evidence of Pyongyang's soldiers being sent to Russia, following previous reports from Ukraine and South Korea.
Kyiv and Seoul say Moscow is planning to involve thousands of North Korean troops in its full-scale war.
"If they do deploy to fight against Ukraine, they're fair game, they're fair targets, and the Ukrainian military will defend themselves against North Korean soldiers the same way they're defending themselves against Russian soldiers," Kirby told a press briefing at the White House.
"And so the possibility that there could be dead and wounded North Korean soldiers… is absolutely real if they get deployed."
Kirby also revealed details of U.S. intelligence assessments, saying Washington believes North Korea "moved at least 3000 soldiers into eastern Russia."
"We assess that these soldiers traveled by ship from the Wan area in North Korea to Vladivostok, Russia," he said, adding: "These soldiers then traveled onward to multiple Russian military training sites in eastern Russia where they are currently undergoing training."
Kirby said it was too early to say for sure if they "will enter into combat alongside the Russian military," but added it was a "highly concerning probability."
" We have briefed the Ukrainian government on our understanding of this situation, and we're certainly consulting closely with other allies, partners and countries in the region on the implications of such a dramatic move, and on how we might respond," he said.
"I expect to have more to share on all of that in the coming days."
Kyrylo Budanov, head of Ukraine's military intelligence (HUR), said that the first North Korean units were expected to arrive in Kursk Oblast on Oct. 23 . Ukraine began a cross-border incursion in August and still holds significant swathes of territory there.
Earlier in October, Budanov said that the first group would consist of 2,600 soldiers.
Two North Korean brigades of up to 6,000 personnel each are currently undergoing training in Russia, President Volodymyr Zelensky said.
According to military intelligence, some North Korean officers are already in the occupied territories of Ukraine, he said on Oct. 17.
North Korea has denied the reports, while a Kremlin spokesperson gave an evasive answer on the issue.
A military intelligence source told the Kyiv Independent on Oct. 21 that Russian authorities detained 18 North Korean soldiers who abandoned their positions in Kursk Oblast. Video footage has also circulated purporting to show North Korean troops at a Russian military training camp.
South Korean media reported on Oct. 22 that Pyongyang has dispatched pilots who can fly Russian warplanes to join the war in Ukraine. South Korea's Yonhap agency also said that South Korea is considering sending personnel to Ukraine to monitor North Korean troops.