"What we see more and more is that North Korea, Iran, China, and of course Russia are working together, working together against Ukraine," Rutte told reporters at a European leaders' meeting in Budapest.

"This is more and more a threat, not only to the European part of NATO, but also to the United States -- because Russia is delivering the latest technology into North Korea," he warned.

"I look forward to sit down with Donald Trump to discuss how we can face these threats collectively," Rutte said.

North Korea has become one of the strongest backers of Russia's full-scale offensive in Ukraine, and the West has long accused Pyongyang of supplying artillery shells and missiles to Moscow.

Based on intelligence reports, Western powers now believe Pyongyang has deployed around 10,000 troops to Russia, suggesting deeper involvement in the conflict.

Iran meanwhile stands accused of supplying Russia with missiles and drones, while China is suspected of helping Moscow to circumvent Western sanctions on technologies for use in the war against Ukraine.