WASHINGTON — Some 8,000 North Korean soldiers are now in Russia near Ukraine’s border and are preparing to help the Kremlin fight against Ukrainian troops in the coming days, the Biden administration said Thursday.

The new figure is a dramatic increase from a day earlier, when Defense Secretary Lloyd Austin would only say “some” of the troops had moved toward Ukraine’s border in the Kursk region, where Moscow’s forces have struggled to push back a Ukrainian incursion.

That also would mean most of the North Korean troops that the U.S. and its allies say have been sent to Russia are on the Russia-Ukraine border.

The U.S. has estimated there are about 10,000 North Korean troops in Russia. Seoul and its allies assess that the number has increased to 11,000, while Ukraine has put the figure higher, at up to 12,000.

Of the 8,000 in Kursk, “we’ve not yet seen these troops deploy into combat against Ukrainian forces, but we would expect that to happen in the coming days,” Blinken said at a news conference with Defense Secretary Lloyd Austin and their South Korean counterparts.

He said Russia has been training North Korean soldiers in artillery, drones and “basic infantry operations, including trench clearing, indicating that they fully intend to use these forces in front-line operations.”

North Korea’s move to tighten its ties with Russia has raised global concerns about how that may expand the war and what Russian military aid will be delivered in exchange. North Korea also has provided munitions to Russia.

It has become a key topic as U.S. and South Korean leaders met this week in Washington, fueling concerns that the presence of those soldiers will further destabilize the Asia-Pacific and broaden Moscow’s war on Ukraine.

South Korean Foreign Minister Cho Tae-yul condemned the deployment “in the strongest possible terms” and called for an immediate withdrawal of the troops. North Korea’s belligerent actions not only places the European continent but also the Korean Peninsula under threat and that Seoul agrees “to take necessary measures accordingly,” he said.

Also Thursday, North Korea test-fired an intercontinental ballistic missile for the first time in almost a year, demonstrating a potential advancement in its ability to launch long-range nuclear attacks on the U.S.

Some experts speculated Russia may have provided technological assistance to North Korea over the launch.