New START ends. But a one-year extension could bring many benefits

Editor’s note: This is part of an “experts comment” series on the expiration of New START.

President Donald Trump told the New York Times in January that he wants to negotiate a better treaty than New START, a message he repeated on February 5, the day the treaty went out of force. Karoline Leavitt, the White House spokesperson, added, “The president wants to have our nuclear experts work on a new improved and modernized treaty that can last long into the future. And that’s what the United States will continue to discuss with the Russians.”

All of this is welcome. Many have complained that New START does not limit nonstrategic nuclear weapons, nor does it limit so-called Russian exotic weapon systems. It was not designed to do so. The United States’ goal has always been to take up nonstrategic nuclear weapons in the next negotiations, as called for in the resolution of ratification of New START. As for the exotic systems, they appeared on the scene after New START entered into force, and of course, they must be accounted for in any new treaty.

Meanwhile, Russian Foreign Minister Sergey Lavrov has stated that Russia remains committed to maintaining the treaty’s numerical limits for an additional year, in order to avoid a vacuum in strategic stability—provided the United States reciprocates. This, he explained, is intended as a cooling-off period during which tensions could be reduced and conditions created for more substantive discussions. That is also welcome.

Clearly, the United States is right to be concerned about the ongoing modernization of the Chinese nuclear arsenal. But, as I stressed during my December 10 testimony before the Senate Foreign Relations Committee, a one-year extension of New START limits would not prejudice any of the vital steps that the United States is taking to respond to the Chinese nuclear build-up. The United States must continue to plan against this build-up and work carefully to determine what capabilities will be needed, including in the realm of uploading additional warheads. This one-year period would have bought extra time for preparation without the added challenge of Russia, now free from New START limitations, embarking on a rapid upload campaign. That would not be in the US interest.

The Chinese nuclear buildup will be a long-running challenge in the 21^st century, and the United States must address it. The Chinese, however, are still fiercely reluctant to engage the issue, not wanting to limit or reduce their nuclear forces until a certain point in the future, but one that they haven’t communicated to Washington. China may want to build up to the levels of the United States and Russia—thereby creating the two-nuclear-peer problem that worries Washington so much. Or, China wants it the other way around and is waiting until the United States and Russia come down to its level—Beijing’s canonical talking point.

But despite Chinese officials’ refusal to discuss limits or reductions, they seem more open to conversations about constraining nuclear risks. That is why, if I could get to the table tomorrow with Russia and China—or with the five permanent members for that matter^[1]—I would have two priorities.

First, I would start with a serious discussion of permitted activities under the nuclear testing moratorium. Nuclear powers may have different understandings of what is allowed, and their diplomats should discuss these differences in a technical and professional setting, out of the public spotlight, in the interest of achieving the reciprocity that is so important to President Trump. Delegations should also work on a new joint verification experiment, drawing on the legacy of the 1988 US-Soviet Joint Verification Experiment, to bolster mutual understanding of and predictability about permitted activities under the moratorium.

In 1988, the United States and the Soviet Union visited each other’s test sites to cooperate in instrumenting and conducting explosive nuclear tests. The goal was to clarify monitoring methods for the Threshold Test Ban Treaty. A new joint experiment would not involve explosive nuclear tests, but it could allow the two sides together to instrument and conduct subcritical nuclear experiments. In this case, China could also be involved, and that would allow the three largest nuclear-weapon states under the Nonproliferation Treaty to develop a better reciprocal understanding of the nuclear testing moratorium. The other nuclear weapon states, France and the United Kingdom (and eventually other states possessing nuclear weapons, prominently India and Pakistan) could engage as well. Such joint activities would be a big step toward reducing nuclear risk.

The second priority would be to get down to business in talking about how to manage integrated air and missile defense requirements, given the wide missile proliferation that has become evident in the Ukraine war and other current conflicts—even among non-state actors, such as the Houthis in the Red Sea.^[2] Diplomats and arms control experts must think hard about how to build defenses against drones and missiles of multiple ranges, many of which will be capable of launching either nuclear or conventional warheads. At the same time, we must ensure that strategic nuclear forces remain a viable means to deter nuclear attacks. This is a common problem that affects all states deploying strategic offensive forces, not just the United States and Russia.

I am not calling for negotiating a new Anti-Ballistic Missile Treaty. I am talking about how to sustain the viability of strategic offensive deterrence while deploying capable integrated air and missile defense. Perhaps new technologies will help here, or perhaps it will be clarity and information-sharing about the nature of the defensive systems being deployed—but speaking candidly about what nuclear-weapon states consider needed to defend themselves will be important to all such states deploying strategic nuclear deterrent forces.

As the Strategic Posture Commission recommended, I support building integrated air and missile defenses against a limited conventional or nuclear coercive attack. However, I do not support the United States spending national resources to try building a comprehensive strategic defense system, like Reagan’s “Star Wars” program in the 1980s. Not only would it be a resource sink, but it would also be destabilizing and fueling a new nuclear arms race.

Notes

[1] The UN Security Council’s five permanent members, or P5, are the nuclear-weapon states under the Nuclear Non-Proliferation Treaty: the United States, Russia, China, the United Kingdom, and France.

[2] Another important discussion should be about banning nuclear weapons on short- and intermediate-range missile systems, but that discussion is a longer-term prospect that should extend well beyond the P5. E.g., see Rose Gottemoeller, “Nuclear Arms Control Enters Uncharted Territory. It Needs Tools-Both Old and New,” Bulletin of the Atomic Scientists, July 30, 2025, https://thebulletin.org/2025/07/nuclear-arms-control-enters-uncharted-territory-it-needs-tools-both-old-and-new/