South Korea’s military says it suspects North Korea is preparing to send additional troops to Russia after its soldiers already deployed on the Russian-Ukraine war fronts suffered heavy casualties.

Russia signed a strategic partnership treaty with Iran on Friday that follows similar pacts with China and North Korea. All three countries are adversaries of the United States, and Russia has used its ties with them to help blunt the impact of Western sanctions and boost its war effort in Ukraine.

North Korea may be accelerating plans to send more troops to replace frontline casualties incurred fighting Ukraine on behalf of Russia.