U.S. confirms North Korean troops are in Russia. What it means for the war in Ukraine.

U.S. officals said Wednesday that North Korea has deployed thousands of troops to Russia, confirming claims by Ukrainian and South Korean officials that Pyongyang is aiding Moscow with manpower amid Russia’s ongoing war with Ukraine.

"We are seeing evidence that there are North Korean troops that have gone to Russia," Defense Secretary Lloyd Austin told reporters traveling with him in Rome. "What, exactly, they're doing is left to be seen. These are things that we need to sort out."

At the White House, National Security Council spokesman John Kirby said that U.S. intelligence officials have determined that North Korea moved at least 3,000 soldiers by ship into eastern Russia earlier this month. The soldiers then traveled to multiple training sites in eastern Russia where they are currently undergoing training.

"We do not yet know whether these soldiers will enter into combat alongside the Russian military," Kirby said. "But this is certainly a highly concerning probability."

How did we get here?

Russian President Vladimir Putin met with North Korean leader Kim Jong Un in Pyongyang in June. The two sides emerged from the summit with a strategic agreement expanding their economic and military cooperation.

Late last week, Ukrainian President Volodymyr Zelensky accused North Korea of sending a military delegation to Russia and preparing to send 10,000 soldiers to help Moscow's war effort.

South Korea's National Intelligence Service said North Korea had shipped 1,500 special forces to Russia for training and eventual deployment in the war.

North Korean and Russian officials denied the reports of North Korean troops in Russia. U.S. officials were unable to confirm them until Wednesday.

What it means for the war

North Korea has one of the largest militaries in the world with over 1 million active personnel.

Russia has already used dozens of North Korea-made ballistic missiles against Ukraine, according to Reuters, and has received arms and munitions from Pyongyang.

But the use of North Korean troops on the ground in Russia’s fight against Ukraine would be an escalation in its war, now in its third year.

"That is a very, very serious issue," Austin added. "And it will have impacts not only in Europe, it will also impact things in the Indo-Pacific as well."

It's also an indication that the bloody conflict has taken a toll on Russia's military. U.S. military officials estimate that more than 600,000 Russian troops have been killed or wounded since the war began, in 2022.

"You've heard me talk about the significant casualties that [Putin] has experienced over the last two and a half years," Austin said. "This is an indication that he may be even in more trouble than most people realize."

"Let's be clear," Kirby said. "If North Korean soldiers do enter into combat, this development would demonstrate Russia's growing desperation in its war against Ukraine."

He added: "If Russia is forced to turn to North Korea for manpower, this is a sign of weakness, not strength, on the part of the Kremlin."

What's next?

Austin said Wednesday that the U.S. would continue to monitor the troop buildup to assess why they are there — and whether North Korea can be considered a "co-belligerent" in the war.

The U.S. recently announced that it would provide more than $800 million in additional security assistance to Ukraine.

And Kirby said the U.S. is "on track" to provide Ukraine with hundreds of air-defense systems, artillery, armored personnel carriers and infantry fighting vehicles — "all of which will help keep Ukraine effective on the battlefield."