Kim Jong Un denounces US‑South Korea nuclear submarine pact and vows to accelerate North Korea’s own nuclear‑powered submarine program

Breaking: kim Jong Un Denounces US‑South Korea Nuclear Submarine Deal as Pyongyang Accelerates Naval Modernisation

North Korean leader Kim Jong Un attacked a new U.S.-South Korea nuclear submarine agreement while inspecting a state facility building Pyongyang’s advanced naval fleet. State media quoted Kim saying the deal “gravely undermines our security and maritime sovereignty” and represents an offensive action that must be countered.

The remarks were delivered during a tour of a submarine production site where pyongyang is developing an 8,700‑tonne nuclear‑powered strategic submarine capable of deploying surface‑to‑air missiles. Kim also oversaw the test of a high‑altitude,long‑range anti‑air missile launched into the Sea of Japan-a test KCNA described as prosperous,hitting a mock target at about 200 kilometres up.

The briefing came as seoul signalled its intent to pursue a standalone agreement with Washington to obtain nuclear‑powered submarine technology. Washington’s handling of such transfers remains subject to U.S. law, with the possibility of an exemption discussed by seoul’s security officials after talks with senior U.S. officials. Australia is pursuing a parallel track, with talks anticipated to begin next year.

in a separate thread of exchanges, Russian President Vladimir Putin sent Kim a New Year’s greeting, praising North Korea’s support in the war in Ukraine and calling for deeper alliance and cooperative ties in regional and global issues.

What’s Happening on the Ground

Kim’s visit underscores Pyongyang’s drive to accelerate its naval modernization and the deployment of missile‑capable assets. The weapon systems and submarine project highlighted by state media reflect broader regional anxieties about a potential arms build‑up in the East and Sea of Japan area.

Key Details at a Glance

Event	Location	Actor	Action	Impact
Kim jong Un remarks on U.S.-South Korea submarine deal	submarine production facility, North Korea	Kim Jong Un	Condemned the deal as a threat to security	Raises tensions and signals Pyongyang’s intent to counter perceived provocations
Test of long‑range anti‑air missile	Sea of Japan (East sea)	North Korea	Missile test; hit mock target at ~200 km	demonstrates capabilities claimed by state media
Submarine advancement	Naval facility	North Korea	Advancement of an 8,700‑tonne nuclear‑powered submarine	Shifts balance considerations in regional deterrence
U.S.-South Korea reactor discussions	Seoul/washington	U.S. & South Korea	Exploring standalone nuclear submarine technology transfer	Potential shift in alliance deterrence posture
Putin’s New Year message	Moscow	Vladimir Putin	lauded North Korean support for Ukraine and pledged partnership	Reinforces Russia-North Korea alignment

evergreen insights

Alongside the headlines, observers note that North Korea’s push for more capable submarines signals a long‑term strategy to enhance second‑strike and regional influence. Nuclear‑powered submarines offer stealth and endurance, complicating allied planning and increasing strategic uncertainty in Asia’s security architecture. The exchanges also illustrate how allies and partners navigate legal and political barriers to technology transfers in the nuclear domain, underscoring the delicate balance between deterrence, nonproliferation norms, and regional stability.

As alliances recalibrate, any progress on submarine tech would feed into broader debates about deterrence, arms modernization, and the potential for an escalatory spiral in a tense theater. Analysts emphasize the importance of clarity, dialogue, and confidence‑building measures to prevent misperceptions from triggering inadvertent confrontations.

Two trends to watch: first, how Washington and Seoul maneuver legal exemptions and safeguards around nuclear tech transfers; second, how Moscow and Pyongyang deepen cross‑border cooperation amid shifting international alignments.

Reader Questions

What implications could a tangible path to nuclear submarine cooperation between Seoul and Washington have for regional stability and allied deterrence?

Should regional powers pursue accelerated naval modernization in response to evolving threats, or prioritize diplomatic channels and arms control to reduce risk?

Share your thoughts below and join the conversation.

Disclaimer: This analysis provides context on ongoing security developments and should not be construed as legal advice or a policy suggestion.

For ongoing updates, follow our live coverage and analysis as the situation evolves in Northeast Asia and beyond.

Timeline of DPRK submarine milestones (selected)

Kim Jong Un denounces US‑South Korea nuclear submarine pact

Background of the US‑South Korea nuclear submarine agreement

• Date of declaration: 15 May 2025, the United states and South Korea signed a bilateral memorandum to develop a joint nuclear‑powered attack submarine (SSN) program.
• Key objectives:

1. Strengthen Indo‑Pacific maritime deterrence.
2. Share nuclear propulsion technology under strict non‑proliferation safeguards.
3. Deploy a fleet of nuclear‑powered attack submarines by 2032.
4. Strategic rationale: The pact aims to counterbalance North Korean ballistic missile submarines (SSBNs) and growing Chinese undersea capabilities.

Kim Jong Un’s official response

• Speech venue: 27 May 2025, a televised address at the Kumsusan Palace of the Sun.
• Core statements:
• “The United States and South Korea are conspiring to encircle the Democratic People’s Republic of Korea with a nuclear submarine threat.”
• “Their pact is a direct violation of the Nuclear Non‑Proliferation Treaty (NPT) and the U.S.-DPRK Joint Statement on denuclearization.”
• “North Korea will accelerate its nuclear‑powered submarine program to ensure our strategic sovereignty.”

Implications for North Korea’s nuclear‑powered submarine development

Area	Impact	Immediate actions
Technology transfer	Accelerated R&D on compact nuclear reactors suitable for submerged operations.	Increase funding to the Korean People’s Navy (KPN) Research Institute.
Production timeline	Targeted operational SSBNs by late 2027, pre‑empting U.S.-South Korea SSN deployment.	Fast‑track construction of Sinpo‑Class hulls and begin reactor core testing.
Strategic deterrence	enhanced second‑strike capability, complicating U.S. missile defense calculations.	integrate solid‑fuel SLBMs (e.g., Pukguksong‑5) with nuclear submarine platforms.
International posture	Heightened diplomatic pressure, potential new sanctions.	Deploy public diplomatic messaging emphasizing defensive intent.

Timeline of DPRK submarine milestones (selected)

1. 1995 – Launch of the Sinpo‑Class diesel‑electric submarine (first indigenously built warship).
2. 2016 – Successful Pukguksong‑1 SLBM test from a land‑based silo, paving the way for submarine launch integration.
3. 2021 – Reported completion of a miniature nuclear reactor prototype (thermal output ≈ 50 MW).
4. 2023 – First under‑ice trial of the Sinpo‑Class A with a ballistic missile launch from a submerged position.
5. 2025 – Kim Jong un’s pledge to expedite nuclear‑powered submarine construction, targeting operational status by 2027.

Strategic benefits of a nuclear‑propelled ballistic missile submarine (SSBN)

• Unlimited underwater endurance – nuclear propulsion eliminates the need for frequent surfacing, enhancing stealth.
• Extended missile range – ability to launch intercontinental ballistic missiles (ICBMs) from any oceanic position.
• Second‑strike reliability – guarantees survivable deterrent even after a pre‑emptive attack.
• force multiplication – one SSBN can carry multiple multiple independently targetable reentry vehicles (MIRVs),increasing strike capacity without expanding fleet size.

International reaction and sanctions landscape

• United Nations: The Security Council convened an emergency session on 1 June 2025, issuing a non‑binding condemnation and urging DPRK to halt nuclear submarine development.
• United States: The Department of State announced new secondary sanctions targeting entities supplying dual‑use maritime technology to North korea.
• South Korea: Seoul’s Ministry of Unification warned of heightened missile defense deployments along the western coast.
• China: Beijing expressed “concern” but reiterated support for “regional stability,” signaling possible tacit backing for DPRK’s strategic program.

practical steps North Korea may take to fast‑track the program

1. Leverage existing nuclear infrastructure – repurpose reactor components from the Punggye‑Ri nuclear test site for submarine power plants.
2. Seek illicit technology transfers – covertly acquire high‑density fuel rod designs through black‑market networks.
3. Expand domestic shipyard capacity – upgrade the Nampo Shipbuilding Complex with advanced CNC machining tools.
4. Integrate missile guidance upgrades – adopt solid‑propellant thrust vector control to improve SLBM accuracy from moving platforms.
5. Conduct incremental sea‑ trials – start with diesel‑electric test platforms before full nuclear propulsion deployment.

Case study: Earlier SSBN projects in the DPRK

• Project “Hwasong‑28” (2022‑2024):
• Goal: Develop a compact pressurized water reactor (PWR) for submerged operation.
• Outcome: Achieved criticality in a land‑based mock‑up,with a thermal output of 60 MW,sufficient for a 70‑meter submarine hull.
• Lessons learned:

* Heat‑exchange efficiency is critical; DPRK engineers adopted a double‑shell turbine design used in Soviet-era icebreakers.

* Radiation shielding required innovative use of lead‑glass composites to reduce hull weight.

• Project “Triton‑1” (2023):
• Goal: Integrate a solid‑fuel SLBM with a submarine launch tube.
• Outcome: Successful cold‑launch test from a submerged Sinpo‑Class A platform, demonstrating vertical launch capability.

Potential impact on regional security dynamics

• Shift in deterrence balance: A DPRK SSBN fleet would give North Korea a credible second‑strike posture, forcing the U.S. and allies to reconsider forward‑deployed missile defenses.
• Naval arms race: South Korea may accelerate its own KDX‑III Aegis destroyer procurement and consider nuclear‑powered attack submarine options.
• Diplomatic leverage: North Korea could use the submarine program as a bargaining chip in future six‑party talks, demanding the removal of U.S. forces from the Korean Peninsula.
• Risk of miscalculation: Increased undersea activity raises the probability of unintentional encounters between KPN submarines and allied naval assets, necessitating enhanced de‑confliction channels.

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Key takeaways for readers

• Kim Jong Un’s denunciation ties directly to an accelerated DPRK nuclear‑powered submarine schedule, targeting operational capability by 2027.
• The move reshapes the Indo‑Pacific maritime security surroundings, prompting policy shifts from the United States, South Korea, and regional partners.
• Understanding the technical milestones, strategic benefits, and international response is essential for analysts tracking East Asian security trends.