Russian President Vladimir Putin and North Korean leader Kim Jong Un signed a mutual defense assistance pact on Wednesday during Putin’s visit to the North Korean capital Pyongyang since 2000.

According to a statement from the Russian government, the Treaty on Comprehensive Strategic Partnership stipulates “mutual assistance in the event of aggression against one of the parties thereto.” Putin characterized the deal as a “breakthrough document,” reflecting the desire to elevate relations to a “new qualitative level.”

Putin further criticized the US’s “confrontational policy” in the region, which he says is “accompanied by a substantial increase in the scope and intensity of various military exercises involving the Republic of Korea and Japan, which have a hostile nature towards the DPRK [the Democratic People’s Republic of Korea, commonly known as North Korea].”

The treaty replaces previous agreements signed in 1961, 2000, and 2001. Notably, the 1961 treaty between the Soviet Union and North Korea stipulated automatic military intervention if either nation came under attack. The 1961 treaty was discarded after the collapse of the Soviet Union, and a 2000 treaty did not stipulate a military alliance between the two countries, but it signified the revival of a more positive Russian stance towards North Korea.

While the full scope of the new pact remains undisclosed, the deepening military ties between Russia and North Korea have raised concerns among Western nations about the potential implications for regional security and ongoing conflicts.

As tensions escalate on the Korean Peninsula, NATO Secretary General Jens Stoltenberg warned that Russia’s war in Ukraine is “propped up” by countries like North Korea, cautioning, “If they succeed in Ukraine, it will make us more vulnerable and the world more dangerous.” The US Department of State previously issued a statement in January condemning North Korea’s export and Russia’s procurement of ballistic missiles as a “flagrant violation” of UN Security Council resolutions.

Article 51 of the UN Charter permits collective self-defense if an armed attack occurs against any member state. Both the prohibition of unilateral use of force and the self-defense exception are fundamental principles of customary international law. However, complexities arise when the attack has ceased or when a state seeks to defend itself against potential future threats. In such situations, the use of force can serve preventive, punitive, deterrent, or combined purposes, leading to varied justifications and implications.

Additionally, any military cooperation that enhances North Korea’s capabilities could be seen as a violation of existing international sanctions imposed on the country, particularly those related to its ballistic missile and nuclear programs.

With Russia wielding veto power on the UN Security Council, there are mounting concerns that strengthened ties may further weaken controls on North Korea’s weapons program. In March, Russia vetoed the renewal of a UN expert panel monitoring North Korean sanctions, drawing accusations of seeking to avoid scrutiny of arms deals between Moscow and Pyongyang.