By Leonam dos Santos Guimarães*
RIO DE JANEIRO | 24 April 2025 (IDN) — Since 2020, the international nuclear non-proliferation and nuclear test ban regime has encountered unprecedented and systemic challenges. The resurgence of geopolitical rivalries, the modernization and expansion of nuclear arsenals, and the erosion of long-standing arms control commitments have brought nuclear weapons back to the forefront of international security discourse, in a manner not seen since the Cold War.
Amid this evolving landscape, key states are increasingly prioritizing nuclear deterrence, while crucial multilateral treaties face mounting pressures and setbacks. International institutions, traditionally tasked with maintaining oversight and enforcement of non-proliferation norms, are struggling to respond effectively to these new threats.
This article examines the key dynamics shaping the current moment by analysing: (1) the actions of pivotal states — Russia, China, the United States, Iran, and North Korea — in the nuclear domain; (2) the status and vulnerabilities of key treaties, including the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), the Comprehensive Nuclear-Test-Ban Treaty (CTBT), and the Treaty on the Prohibition of Nuclear Weapons (TPNW); and (3) the role and limitations of international institutions such as the United Nations Security Council (UNSC) and the International Atomic Energy Agency (IAEA). It concludes with a comprehensive assessment of the systemic risks now confronting this critical regime.
1. Actions of Key States
Russia
Russia’s recent actions have deeply unsettled the pillars of nuclear arms control. In February 2023, Moscow announced the suspension of its participation in the New START Treaty, the last remaining bilateral agreement with the United States regulating strategic nuclear arsenals. Although not a formal withdrawal, the suspension effectively dismantles the last significant constraint on the world’s two largest nuclear powers, responsible for nearly 90% of global warheads.
Compounding these concerns, Russia rescinded its ratification of the CTBT in October 2023, citing the United States’ failure to ratify the treaty. Despite assurances that a moratorium on nuclear testing would be maintained, the revocation marks the first time since 1990 that Russia has openly disengaged from a nuclear testing commitment. Preparations at nuclear testing facilities, including orders from President Vladimir Putin to ensure readiness, further heighten fears of a potential resumption of nuclear tests.
In parallel, Russia has adopted increasingly aggressive nuclear posturing during its invasion of Ukraine. Notably, Moscow deployed tactical nuclear weapons to Belarus — the first transfer of such weapons outside Russian territory since the dissolution of the Soviet Union — and made repeated nuclear threats aimed at deterring Western support for Ukraine. Moreover, the military occupation of Ukraine’s Zaporizhzhia Nuclear Power Plant created severe nuclear safety risks and obstructed international diplomatic efforts, including at the 2022 NPT Review Conference.
Collectively, these actions have eroded key norms underpinning non-proliferation and test ban efforts and signal a readiness by Russia to leverage nuclear threats as a tool of coercion in conflict.
China
Although less overtly confrontational, China’s nuclear posture has evolved significantly since 2020. Beijing has embarked on a rapid expansion and modernization of its nuclear forces, with independent estimates suggesting a near doubling of its warhead stockpile from approximately 280 in 2018 to around 470 by 2024. Satellite imagery has revealed the construction of over 300 new ICBM silos, indicating an unprecedented build-up in China’s strategic forces.
Despite being a CTBT signatory, China has not ratified the treaty, conditioning its ratification on reciprocal actions by the United States. Its continued non-ratification leaves the CTBT’s entry into force in a precarious state. Furthermore, China has repeatedly declined invitations to engage in trilateral arms control discussions with the United States and Russia, citing disparities in arsenal size.
China officially maintains its commitment to the NPT and has supported regional nuclear-weapon-free zones. However, its growing nuclear arsenal and reluctance to engage in new arms control measures contribute to strategic instability. In a context where the United States and Russia already possess expansive arsenals, China’s expansion risks fueling a multi-polar nuclear competition without effective regulatory frameworks.
United States
The United States, historically a principal architect of the non-proliferation regime, has made decisions in recent years that have both reinforced and strained this framework. During the Trump administration, serious consideration was given to resuming nuclear testing — a move that would have shattered a near three-decade-long moratorium. Although no test occurred, the mere discussion revealed a weakening political commitment to the CTBT.
The U.S. Senate’s continued refusal to ratify the CTBT remains a major impediment to the treaty’s entry into force. Furthermore, the 2018 withdrawal from the Joint Comprehensive Plan of Action (JCPOA) — the nuclear agreement with Iran — undermined diplomatic efforts to contain Tehran’s nuclear program and fractured the unity of the international community on non-proliferation enforcement.
While the Biden administration extended New START until 2026 and has sought to revive multilateral diplomacy, challenges persist. The U.S. remains opposed to the TPNW, arguing that the treaty could undermine existing security frameworks by neglecting the realities of nuclear deterrence. Moreover, modernization programs for U.S. nuclear forces continue apace, revealing a paradox: while advocating for non-proliferation, the United States also engages in a renewed technological nuclear competition.
Iran
Iran has emerged as a central concern in the post-2020 non-proliferation landscape. Following the U.S. withdrawal from the JCPOA, Tehran progressively breached the agreement’s limits, enriching uranium to 60% — well beyond civilian needs and near weapons-grade levels. By late 2024, Iran had accumulated sufficient enriched material that, if further processed, could produce enough fissile material for several nuclear weapons within weeks.
Compounding these concerns, Iran has curtailed the IAEA’s enhanced monitoring activities since 2021, limiting transparency and oversight. Expulsions of key inspectors in 2023 further deteriorated the verification environment, prompting warnings from the IAEA Director General that the agency’s ability to assure the peaceful nature of Iran’s program was increasingly compromised.
Diplomatic efforts to restore the JCPOA have failed, and although informal understandings have attempted to limit further escalation, the absence of a formal agreement leaves the situation precarious. Regional powers, such as Saudi Arabia, have openly indicated that an Iranian nuclear weapon would compel them to pursue similar capabilities, raising the specter of a nuclear arms race in the Middle East.
North Korea
North Korea remains the most overt case of nuclear proliferation. Although no nuclear tests have been conducted since 2017, preparations for a seventh test have been underway since at least 2022. Meanwhile, Pyongyang has carried out an unprecedented number of ballistic missile launches, including intercontinental-range systems capable of reaching the United States.
Domestically, North Korea has enshrined its nuclear-armed status into law, explicitly authorizing the use of nuclear weapons in a wide range of scenarios, including pre-emptive strikes. Pyongyang’s consolidation of its nuclear posture signals the abandonment of any serious denuclearization dialogue.
The paralysis of the UN Security Council, owing to vetoes by China and Russia, has allowed North Korea’s violations to go largely unpunished, undermining international norms and encouraging other potential proliferators.
2. Status and Challenges of Key Treaties
Treaty on the Non-Proliferation of Nuclear Weapons (NPT)
The NPT remains the cornerstone of the international non-proliferation regime, but it faces growing stresses across all three of its pillars: non-proliferation, disarmament, and the peaceful use of nuclear energy.
The failure of successive Review Conferences (2015 and 2022) to produce consensus documents highlights deepening divisions. Disputes over regional conflicts, such as the war in Ukraine, have further politicized the NPT forum. Meanwhile, frustrations over the slow pace of nuclear disarmament have fueled support for alternative approaches, such as the TPNW.
Concerns over regional proliferation, especially in the Middle East and Northeast Asia, threaten to erode the NPT’s credibility. Without renewed political commitment and tangible progress, the risk grows that states may lose faith in the regime’s effectiveness.
Comprehensive Nuclear-Test-Ban Treaty (CTBT)
The CTBT, although widely respected in practice, has not entered into force, leaving a significant gap in the legal prohibition of nuclear testing. The revocation of Russia’s ratification in 2023, coupled with persistent non-ratification by the United States and China, casts doubt over the treaty’s future viability.
North Korea’s potential resumption of nuclear testing would further undermine the global moratorium. Should major powers follow suit, the world could see a return to competitive nuclear weapons development based on new, untested designs — an outcome the CTBT sought to prevent.
Treaty on the Prohibition of Nuclear Weapons (TPNW)
The TPNW represents a normative challenge to the traditional non-proliferation architecture. While widely supported by non-nuclear-armed states, it has been boycotted by all nuclear powers and their key allies.
Though the TPNW reinforces the moral stigma against nuclear weapons, its practical impact remains limited in the absence of nuclear-armed states’ participation. Its existence, however, reflects growing impatience among the majority of UN members regarding the slow pace of disarmament and could shape future debates over the legitimacy of nuclear deterrence doctrines.
3. Role and Limitations of International Organizations
United Nations Security Council (UNSC)
The UNSC has historically played a central role in non-proliferation enforcement. However, since 2020, it has become increasingly paralyzed, particularly regarding North Korea and Iran. Rivalries among permanent members, exacerbated by the war in Ukraine, have hindered collective responses to violations of non-proliferation norms.
Without a unified Security Council, the effectiveness of sanctions and the legitimacy of international responses to nuclear threats are significantly weakened.
International Atomic Energy Agency (IAEA)
The IAEA remains a vital technical pillar of the non-proliferation regime. Yet its capacity to ensure compliance depends on member state cooperation and political backing. In cases such as Iran and North Korea, the agency’s ability to verify peaceful uses of nuclear technology has been severely constrained by lack of access and state obstruction.
Despite its professionalism and technical capabilities, the IAEA can only report violations; it lacks the authority to enforce compliance without Security Council action, which has often been lacking in recent years.
Conclusion: Systemic Risks and the Future of the Regime
The international nuclear non-proliferation and test ban regime is experiencing one of the most precarious periods in its history. Renewed great power competition, regional proliferation pressures, the erosion of arms control treaties, and the paralysis of enforcement mechanisms collectively threaten to unravel decades of progress.
Preventing a slide into a new era of nuclear arms racing and proliferation requires urgent and coordinated action. Key steps include revitalizing U.S.-Russia dialogue, engaging China in stability discussions, strengthening verification mechanisms through the IAEA, reinforcing the norm against nuclear testing, and bridging the normative divide between supporters of the NPT and the TPNW.
Without concerted efforts, the erosion of the existing regime will increase the likelihood of nuclear weapons use — a catastrophic outcome for global security and humanity.
*The writer is a nuclear and naval engineer (PhD) and a member of the Brazilian National Academy of Engineering. CEO of Eletronuclear S.A. Coordinator, Brazilian Navy Nuclear Propulsion Program. [IDN-InDepthNews]
Image: A collage of NPT and CTBT images from the Internet.
