The United States will not impose new limits on Ukraine’s use of American weapons if North Korea joins Russia’s war, the Pentagon said Monday, as NATO said North Korea’s military units -Korean had been deployed in the Kursk region in Russia.

North Korea’s deployment fuels Western concerns that the two-and-a-half-year conflict in Ukraine could expand, even as attention turns to the Middle East.

This could indicate that Russia hopes to offset mounting battlefield losses and continue to make slow but steady progress in eastern Ukraine.

“Deepening military cooperation between Russia and North Korea poses a threat to both Indo-Pacific and Euro-Atlantic security,” NATO Secretary General Mark Rutte told reporters after talks with a South Korean delegation on North Korean deployments.

US President Joe Biden said the development was “very dangerous”.

The Pentagon estimates that 10,000 North Korean troops have been deployed to eastern Russia for training, up from an estimated 3,000 troops last Wednesday.

“A portion of these soldiers have already moved closer to Ukraine and we are increasingly concerned that Russia intends to use these soldiers in combat or to support combat operations against Ukrainian forces in Russia’s Kursk oblast, near the border with Ukraine,” Pentagon spokeswoman Sabrina said. Singh, using a term for a Russian region.

The Kremlin initially dismissed reports of a North Korean deployment as “fake news.” But Putin did not deny the presence of North Korean troops in Russia on Thursday and said it was Moscow’s business how to implement a partnership treaty with Pyongyang.

The Russian leader also said over the weekend that Moscow would respond accordingly if the United States and its allies helped Ukraine attack Russia deeply, with Moscow viewing potential Western approval as “direct involvement of the ‘NATO’ in the war.

The United States, however, gave no indication that it would approve Ukraine’s deep strike request.

A North Korean Foreign Ministry official did not confirm media reports of a troop deployment to Russia, but said that if Pyongyang had taken such a step, he believed it would be in line with standards international.

Ukrainian military intelligence announced Thursday that the first North Korean units had been registered in the Kursk border region, where Ukrainian troops have been operating since a major incursion in August.

But the Pentagon refused to confirm that North Korean forces were already present in Kursk.

“It is likely that they are heading in that direction towards Kursk. But I don’t have any more details yet,” Singh said.

Ukrainian President Volodymyr Zelenskiy said the move was an escalation by Russia.

Ukrainian Foreign Minister Andrii Sybiha said kyiv had been warning about the deployment for weeks and accused its allies of failing to provide a firm response.

“The bottom line: listen to Ukraine. The solution: lift restrictions on our long-range strikes against Russia now,” he said on X.

Since their leaders met in the Russian Far East last year, North Korea and Russia have strengthened their military ties. They met again in June to sign a comprehensive strategic partnership including a mutual defense pact.

A series of bilateral visits by senior officials followed between the two countries, which share a small piece of the border. North Korean Foreign Minister Choe Son Hui left Pyongyang on Monday for her second trip to Russia in six weeks.

Rutte said the deployment of North Korean troops was a sign of “increasing desperation” on Putin’s part, Rutte said.

“More than 600,000 Russian soldiers have been killed or injured in Putin’s war and he is unable to continue his assault on Ukraine without foreign support,” Rutte said.

The Ukrainian president’s chief of staff, Andriy Yermak, said sanctions alone would not be a sufficient response to North Korean involvement.

He added that kyiv needed “weapons and a clear plan to prevent further involvement by North Korea.”

“The enemy understands strength. Our allies have this strength,” Yermak said on X.