Several thousand North Korean soldiers have arrived in Russia’s western Kursk region, where they are expected to participate in a coming counteroffensive meant to dislodge the Ukrainian troops who have occupied a portion of the region since August, one Ukrainian and two U.S. officials said Friday.

The North Korean troops have not yet entered the fight, and it is not yet clear what role they will play, the officials said, speaking on the condition of anonymity to discuss sensitive intelligence matters. Whatever their role, the officials said, any significant contingent of North Korean troops will allow Russia to keep more of its forces in eastern Ukraine, where they can stay focused on seizing as much Ukrainian territory as possible before the harsh winter weather sets in.

For weeks, the governments of South Korea and Ukraine have warned that thousands of North Koreans were training alongside Russian soldiers, with Ukraine putting the figure as high as 12,000 troops. And this week, U.S. officials confirmed that a contingent of North Korean troops had been transported by ship to Vladivostok, a large Russian city on the Pacific Ocean, in what U.S. Defense Secretary Lloyd Austin called a “very, very serious” escalation.

On Wednesday, the first North Korean troops had made the nearly 4,000-mile journey to the Kursk region, with thousands more arriving each day since. A senior Ukrainian official with knowledge of the troop movements said that as many as 5,000 North Korean troops were expected to have mustered by Monday.

The troops, according to the officials, are part of an elite unit of the Korean People’s Army. They are being flown from Vladivostok aboard enormous Il-76 transport planes to a military airfield in western Russia, then driven into the battle zone, the Ukrainian official said.

There were mixed signals about whether additional North Korean troops would be sent to fight on Ukrainian territory, the Ukrainian official said. At the moment, they are only concentrating in the Kursk region.

Ukrainian troops entered the Kursk region in early August, taking about 400 square miles of territory in the initial weeks of the incursion. But throughout October, Russian forces have been ratcheting up their attacks on Ukrainian positions in the region, taking back several villages, although Ukraine still occupies about 250 square miles.

But after more than two months on Russian soil, Ukraine has so far failed to achieve one of its main goals in Kursk: diverting Russian troops from the fight in the Donbas region of Ukraine, where they are pushing back Ukrainian forces with slow but steady advances.

On Friday, Ukrainian President Volodymyr Zelenskyy, citing his intelligence services, said the North Korean troops would be deployed to the battlefield as early as next week.

“This is an obvious escalatory step by Russia,” Zelenskyy said.

How the addition of North Korean troops might change the dynamic on the battlefield, if at all, is unclear.

North Korean troops have not fought in any wars since the 1950s, and there are questions about the capabilities of even its elite units. Even before they take to the battlefield, they will have to contend with a language barrier, unfamiliar terrain and army customs that might be far different from their own.

If sent to the front lines in Kursk, they will face a battle-hardened Ukrainian force that Russian troops have been unable to expel since their surprising incursion in August.

“I don’t expect them to be a highly effective fighting force, if they end up on the front,” Emil Kastehelmi, a military expert at the Finland-based Black Bird Group, wrote on the social platform X. But, he added, that might not be the point.

“Someone has to die on the battlefield, and from the Russian viewpoint, it’s of course better if the someone is not Russian,” Kastehelmi said.