WASHINGTON >> Defense Secretary Lloyd Austin said Wednesday that North Korean troops wearing Russian uniforms and carrying Russian equipment are moving toward Ukraine, in what he called a dangerous and destabilizing development.

Austin was speaking in Washington with South Korean Defense Minister Kim Yong-hyun, as concerns grow about Pyongyang’s deployment of as many as 12,000 troops to Russia.

The U.S. and South Korea say some of the North Korean troops are heading to Russia’s Kursk region on the border with Ukraine, where the Kremlin’s forces have struggled to push back a Ukrainian incursion.

Some North Korean advance units have already arrived in the Kursk region, and Austin said “the likelihood is pretty high” that Russia will use the troops in combat. North Korea’s move to tighten its relationship with Russia has triggered alarms across the globe, as leaders worry about how it may expand the war in Ukraine and what Russian military aid will be delivered to Pyongyang.

Ukraine’s U.N. Ambassador Sergiy Kyslytsya, speaking at an emergency meeting of the U.N. Security Council on Wednesday, said they expect as many as 4,500 North Korean troops to be at the border this week and to begin directly participating in combat operations against Ukrainian forces in November.

Asked if it could prompt other nations to get more directly involved in the conflict, Austin said that it could “encourage others to take action” but provided no details.

“This is something that we’re going to continue to watch, and we’re going to continue to work with our allies and partners to discourage Russia from employing these troops in combat,” Austin said.

Kim said he doesn’t necessarily believe the deployment will trigger war on the Korean Peninsula but could increase security threats.

There is a “high possibility” that Pyongyang would ask for higher technologies in exchange for its troops, such as receiving tactical nuclear and ballistic missile capabilities, he said through an interpreter.

Both Kim and Austin called on North Korea to withdraw its troops.

Russia has had to shift some resources to the Kursk border region to respond to Ukraine’s offensive. U.S. leaders have suggested that the use of North Korean forces to augment Russia’s defenses indicates that Moscow’s losses during the more than two-year war have significantly degraded its military strength.

“They’re doing this because (Russian President Vladimir) Putin has lost a lot of troops,” Austin said, adding that Moscow has a choice between mobilizing more of its own forces or turning to others for help.

Russia has sought military weapons from other nations. Those include North Korea and Iran.