North Korea’s top diplomat is set to hold talks in Moscow on Wednesday following reports that Pyongyang has sent thousands of troops to Russia to support its action in Ukraine.

Foreign Minister Choe Son Hui’s arrival followed the Pentagon’s statement that North Korea has deployed about 10,000 troops to Russia to fight against Ukraine within “the next several weeks.”

Maj. Gen. Pat Ryder, the Pentagon press secretary, said Tuesday that a “relatively small number” of North Korean troops are now in the Kursk region, where Russia has struggled to push back a Ukrainian incursion, adding that it’s yet to be seen how Moscow and Pyongyang will use them.

Western leaders have described the North Korean troop deployment as a significant escalation that could also jolt relations in the Indo-Pacific region.

Neither Moscow nor Pyongyang have specified the agenda for Choe’s talks in Moscow, but in a closed-door hearing at South Korea’s parliament, the South’s spy agency said Choe may be involved in high-level discussions on sending additional troops to Russia and negotiating what the North would get in return.

South Korean and Western officials have voiced concern that Russia may offer technology that could advance the threat posed by North Korea’s nuclear weapons and missile programme.

Moscow and Pyongyang have responded vaguely to South Korean and Western claims of the North Korean troop deployment to Russia, emphasising that their military cooperation conforms with international law, without directly admitting the presence of the North’s forces in Russia.

The US and its allies also have accused North Korea of providing millions of artillery shells and other equipment to Russia to fuel its military action in Ukraine.

Russia, along with China, has blocked US-led efforts at the Security Council to tighten sanctions on North Korea over its recent missile testing, which intensified after Russia’s invasion of Ukraine in 2022. Russia also vetoed a UN resolution to extend the mandate of monitors in March, in a move that effectively abolished oversight by UN experts of Security Council sanctions against North Korea.

In a telephone conversation Tuesday with Ukrainian President Volodymyr Zelenskyy, South Korean President Yoon Suk Yeol said deepening military cooperation between North Korea and Russia could pose a “major security threat” to Seoul if the North gains access to Russian technology and its troops get combat experience.

South Korean President Yoon Suk Yeol last week raised the possibility of supplying Ukraine with weapons while saying Seoul is preparing countermeasures that could be rolled out in stages depending on the degree of military cooperation between Pyongyang and Moscow.

South Korea, a growing arms exporter, has provided humanitarian aid and other non-lethal support to Ukraine and joined US-led economic sanctions against Moscow. It has so far resisted calls by Kyiv and NATO to directly supply Ukraine with weapons, citing a longstanding policy of not providing arms to countries engaged in active conflict.