North Korea’s entry into Russia’s war against Ukraine is a major escalation in the grinding conflict, but Moscow may find it’s more trouble than it’s worth.

The recently signed mutual defense treaty could be used to justify thewidening of the war in Ukraine, as the U.S. says North Korean and Russian troops are already battling Ukrainian forces.

“We understand that more than 10,000 North Korean troops are currently in Russia, and a significant number of them have moved to the frontline areas including Kursk,” Jeon Ha-kyou, a spokesperson for Seoul’s defence ministry, told a briefing, citing intelligence authorities.