BRUSSELS — NATO and the European Union are stepping up efforts to persuade China to help North Korea stop sending troops and other support to Russia to support its war in Ukraine.

Up to 12,000 North Korean troops have been sent to Russia’s Kursk border region to help push back Ukrainian forces there, according to assessments by U.S., South Korean and Ukrainian intelligence services. NATO says Russia is sending missile technology to North Korea in return.

As Russia exploits its military advantage in Ukraine, the United States wants its allies to put political pressure on China to rein in North Korea. Since Pyongyang and Beijing established diplomatic ties in 1949, their relationship has been described as being “as close as lips and teeth.”

One policy lever is the threat of increased Western activity in China’s backyard, the Asia-Pacific region. Last week, the EU concluded security agreements with regional powers Japan and South Korea.

In an opinion piece for Politico last week, NATO Secretary General Mark Rutte said that “China bears a particular responsibility here, using its influence in Pyongyang and Moscow to ensure that they put an end to these actions. Beijing cannot claim to promote peace while turning a blind eye to growing aggression.”

During a visit to Latvia on Thursday, Rutte warned that missile technology exchanges in particular pose “a direct threat, not only to Europe, but also to Japan, South Korea and the American continent.” Japan, South Korea, Australia and New Zealand now regularly participate in NATO meetings.

On Wednesday, after talks with US Secretary of State Antony Blinken, he also said that “the Euro-Atlantic space and the Indo-Pacific really need to be seen as one theater, not two separate theaters,” and that “our security, therefore, the situation is now increasingly global and we must view this as a global problem.

While North Korea and Russia have grown significantly closer, many observers say China is reluctant to form an anti-Western three-way alliance with them because it prefers a stable security environment to address economic challenges and maintain its relations with Europe and its Asian neighbors.