The analysis is one of several on the evolving partnership between Russian President Vladimir Putin and North Korean leader Kim Jong Un, said the people, speaking on condition of anonymity to talk about private discussions. They stressed that such a move wasn’t imminent and that military support at that scale — if it occurred — would likely happen in batches with troops rotating over time rather than in a single deployment. 

Ukraine’s ambassador to South Korea made a similar assessment earlier this month. Dmytro Ponomarenko said in an interview with VOA that Kyiv expected up to 15,000 North Korean troops deployed to fight in Russia’s Kursk region – and possibly in occupied areas of eastern Ukraine – to rotate every few months.

Spokespeople for South Korea’s Defense Ministry and Presidential Office didn’t respond to requests for comment.

Kim’s decision to send North Korean troops to join Russia’s fight against Ukraine has alarmed Kyiv’s allies, who’ve warned that it risks exacerbating what is already Europe’s largest conflict since World War II. They believe the deepening cooperation between Putin and Kim could also impact the security balance in the Indo-Pacific region, where there’s mounting rivalry between China and the US.

The issue will be raised by several allies at the G-20 Summit in Brazil this week including by German Chancellor Olaf Scholz when he meets Chinese President Xi Jinping, Bloomberg previously reported. Scholz told Putin Friday in a rare phone call that the deployment of North Korean troops was a “grave escalation” of the war against Ukraine.

Scholz will press the Chinese leader at their meeting in Rio on Tuesday to use his influence over Russia and North Korea to avoid further escalation in the war, according to German officials.

The North Korean deployment shows the war is becoming globalized and Scholz and Xi will need to discuss this new dimension of the conflict, the officials said.

Worries were also raised by allies at the APEC gathering in Lima, Peru, this past week, another person said.

Xi has been the biggest benefactor to Putin and Kim in recent years, and sees both leaders as partners in pushing against the US-led world order. But his government has remained silent publicly on the dispatch of North Korean troops to Russia — a sign the Chinese president may be unhappy with the arrangement.

The Kim-Putin partnership risks adding economic pressure on China, just as Xi is bracing for potential disruption from tariffs threatened by US President-elect Donald Trump when he returns to the White House. It also undermines Beijing’s argument that the US shouldn’t have military alliances in the Indo-Pacific region. 

China doesn’t “allow conflict and turmoil to happen on the Korean Peninsula” and it won’t “sit idly by when its strategic security and core interests are under threat,” Xi told US President Joe Biden at talks Saturday on the sidelines of the Asia-Pacific Economic Cooperation summit in Lima. 

North Korea has so far sent more than 10,000 troops to fight alongside Putin’s army in Russia’s Kursk region, where Ukrainian forces have occupied part of the border territory since a surprise incursion in August. In return, Russia is providing money and helping North Korea increase its capabilities.

South Korea has said there’s a “high chance” that North Korea will seek cutting-edge technology transfers from Russia — including technology related to tactical nuclear weapons, intercontinental ballistic missiles, reconnaissance satellites and ballistic missile submarines.

As well as manpower, North Korea has also sent millions of rounds of artillery ammunition and other weapons to Russia. The Financial Times reported this week, citing Ukrainian intelligence, that Pyongyang has supplied Moscow with long-range rocket and artillery systems too. 

Ukraine has been asking allies for months to allow it to use Western-provided long-range weapons to strike military targets deep inside Russia as a way to counter Moscow’s attacks including on energy infrastructure in the country.