Statement to the Conference on Disarmament

As delivered.

Ministers, Excellencies, Mr. President, thank you for hosting me today. And thank you to Ambassador Zniber for Morocco’s leadership of the CD presidency and stewardship of this year’s High-Level Segment.

A few weeks ago, U.S. Under Secretary for Arms Control and International Security Thomas DiNanno visited the CD to deliver a very important message on a topic that has been at the top of mind for many: what is next for nuclear arms control?

As U/S DiNanno stated, we have now shifted into a new era of nuclear arms control—one that actually addresses the realities of our current security environment.

New START expired on February 5, 2026.

Signed nearly 16 years ago, its numerical limits on warheads and launchers were no longer relevant by the time of its expiration.

For one, Russia violated the treaty from 2022 through to the treaty’s end and stopped implementing the treaty in 2023.

And Russia likely exceeded New START’s central limits at various times over the past few years.

The treaty also did not address Russia’s large arsenal of nonstrategic, or theater, nuclear weapons. This arsenal numbers up to 2,000 warheads and has been a longtime concern for the United States and our allies.

Neither did New START address Russia’s dangerous novel nuclear weapons systems. These include the nuclear-powered, nuclear-armed Skyfall cruise missile and the nuclear-powered, nuclear-armed Poseidon torpedo.

But perhaps its greatest flaw was that New START did not account for the unprecedented, deliberate, rapid, and opaque nuclear weapons buildup by China.

Despite its claims to the contrary, China has deliberately, and without constraint, massively expanded its nuclear arsenal. Without transparency or any indication of China’s intent or endpoint—including in its most recent white paper—we believe China may achieve parity within the next four or five years.

How can we take China’s claim of a no-first-use doctrine seriously, which can in no way be verified, in the midst of such a massive, non-transparent buildup? Similarly, how are we to understand Beijing’s calculation of a “minimum deterrent necessary” if its numbers keep increasing?

China has claimed in the past that it cannot engage the United States in risk reduction because of a lack of trust, yet it expects us and the world to trust that it would not use nuclear weapons first.

At the time of New START’s signing, China had only around 200 nuclear weapons. Now, Beijing is on track to have the fissile material necessary for more than 1,000 nuclear warheads by 2030.

This threat is made worse by Russian assistance to China’s CFR-600 reactors, whereby Russia is transferring highly enriched uranium fuel assemblies to the program that can produce fissile material China needs to help expand its nuclear arsenal.

With China being the only P5 country without a moratorium on fissile material production for weapons purposes, we can see how this could be a problem.

All this to say, New START’s expiration arrived at a fortuitous time – not just for the United States; not even just for the nuclear weapon states – but for all countries, as it allows us to take a renewed push toward President Trump’s ultimate goal of a better agreement.

We could not accept an offer to maintain some of New START’s central limits; asking the United States to confine itself to bilateral limits with Russia—especially while Moscow helps boost Beijing’s capacity to increase its arsenal size and thereby putting upward pressure on U.S. requirements—is the definition of a bad deal.

A few weeks have now gone by since the Treaty’s end. And I think it important to emphasize to you all here today that the Treaty’s expiration—and the absence of any nuclear arms control treaty right now—does not mean the United States is walking away from or ignoring arms control. In fact, quite the opposite is true. It has been President Trump calling for a better agreement. We should all ask ourselves: why have we not seen the rest of the nuclear weapons states joining that call?

The United States is proposing modernized, multilateral strategic stability and arms control discussions. But how we get there can take a variety of forms – there are many different approaches we can take that lead us to our ultimate objective, and we will not foreclose any of those options.

After decades of agreements between the United States and Russia, this transition to a multilateral format is a natural, necessary next step for arms control.

The multilateral approach can prevent an unmitigated nuclear arms race, limit the build-up of nuclear arms, and, as appropriate, address issues surrounding non-NPT states with nuclear weapons.

President Trump has made it clear that other countries have a responsibility to ensure strategic stability, none more so than China, and has kept open the possibility for the involvement of other nuclear-armed states in this effort. He has also made clear that our endpoint—our goal—is a better agreement toward a world with fewer nuclear weapons.

The term “multilateral” can refer to several different venues in which strategic stability and arms control dialogue could take place, and to be frank, as I said, no options are off the table.

The United States is entering this new era with no preconditions, no preconceptions.

We already have one forum, the P5, where NPT-recognized nuclear-weapon States already meet to discuss matters of strategic importance. So we can—and do—talk to each other.

After all, every NPT State Party has an obligation to negotiate in good faith on effective measures relating to nuclear disarmament. Article VI does not say that only those states with the largest arsenals have that responsibility—all five nuclear-weapon States to the NPT share the same obligation.

Since Under Secretary DiNanno’s address, we have received widespread support for this new effort, for which I express my deep appreciation.

We are looking to all of you to help encourage nuclear-weapon States like China and Russia to engage meaningfully in a multilateral process.

Our next steps will be partly informed by how the world responds to our call.

In addition to this new proposal, Under Secretary DiNanno also shared for the first time information about China’s history of nuclear testing. I would like to take this opportunity to further elaborate on his remarks.

As I indicated last week at the Hudson Institute, a probable explosion was detected near the Lop Nur underground nuclear test area as a magnitude 2.75 seismic event at 09:18 Greenwich Mean Time, identified using seismic data from Primary Seismic Station 23—or PS-23 for short—of the International Monitoring System (IMS) network at Makanchi, Kazakhstan.

It was a probable explosion based upon comparisons between historic explosions and earthquakes.

The seismic signals were indicative of a single fire explosion, not typical of mining explosions.

The estimated yield of the event was a 10 tons nuclear explosion—or 5 tons conventional equivalent—which assumes the explosion was fully coupled in hard rock, below the water table, and at the standard scaled depth of burial.

Any deviations from the assumed emplacement conditions (i.e., if the explosion were decoupled or otherwise concealed) would only increase this yield estimate.

Under Secretary DiNanno also shared that we know China has conducted nuclear explosive tests and that we know this test on June 22, 2020, was one such yield-producing nuclear test.

I appreciate that some in this room will not trust U.S. assessments, others will call for more information—and I believe more will be coming—and others know that what I have presented here today is true.

At the end of the day, what matters is that the U.S. government provided information which will help shine light on China’s behavior and spur a discussion on how we all approach responsible nuclear testing behavior going forward.

In addition, China, from the outset, has sought to make it difficult for the international community to monitor China’s testing activities.

During CTBT negotiations on the configuration of the International Monitoring System, Beijing rejected allowing seismic stations to be placed at a comparable distance to its Lop Nur testing site as those the United States permitted near its test site in Nevada. In fact, China required all IMS seismic stations to be located in its east, far from the nuclear test site.

China also delayed certification of two Primary Seismic stations for nearly 20 years and, to date, has not allowed its four Auxiliary Seismic stations to be certified even though they were installed and have been in operation since the 1980s with assistance and collaboration from the United States.

These concerning activities are not the actions of a country that wishes to be transparent about its activities.

In my closing, I want to recognize the role the Conference on Disarmament has historically played in debating and negotiating the concepts and then the elements of arms control arrangements.

Perhaps the CD can once again play a role, if it can only get past what has plagued it for decades: deadlock and an inability to make meaningful progress.

While a treaty limiting nuclear weapons can only come from a negotiation among sovereign states with nuclear weapons, such an agreement affects all of our security.

We are optimistic that CD Member States will rise to the challenge and use the 2026 CD session to recognize the opportunity of today and today’s security environment and how we may all benefit from President Trump’s renewed push for strategic stability.

Ministers and Excellencies, thank you for your attention.