Last Treaty Curbing US, Russian Nuclear Weapons Has Collapsed

The end of the New Strategic Arms Reduction Treaty (New START), the last treaty between the U.S. and Russia placing limits on their respective nuclear arsenals, may not make an arms race inevitable. There is still potential for pragmatic diplomacy.

Both sides can adhere to the basic limits even as they modernize their arsenals. They can bring back some of the risk-reduction measures that stabilized their relationship for years. And they can reengage diplomatically with each other to craft new agreements. The alternative — unconstrained nuclear competition — is dangerous, expensive and deeply unpopular with most Americans.

New START’s legacy

With New START gone as of Feb. 5, the world has lost the last legal check on the U.S.’ and Russia’s nuclear arsenals. These two countries together hold about 90% of all nuclear weapons.

For 15 years, New START has capped those arsenals: no more than 1,550 deployed strategic warheads and 700 deployed delivery systems each. The treaty forced both sides to share information and allow inspections. These measures provided predictability and reduced the risk of miscalculation.

Even as relations between the U.S. and Russia soured, both countries largely stuck to the treaty’s limits. According to a 2024 State Department report, Russia may have briefly exceeded the deployed warhead limit by a small amount, but overall, both sides played by the rules. Now that restraint is a choice, not an obligation.

But the end of New START doesn’t have to mean that an arms race must follow. The size of future arsenals will still depend on politics, budgets, industrial capacity and threat perceptions. And even though inspections stopped a while ago, first because of COVID in 2020, then after Russia suspended its participation in 2023, those limits still influenced both sides’ planning.

Why keep the limits?

As I wrote in my new brief for the Quincy Institute, “Strategic Prudence and Extending New START,” there are strong reasons for both countries to show restraint, even without a treaty forcing their hands. Nuclear weapons are expensive to build and maintain.

The Congressional Budget Office estimated in 2025 that keeping and upgrading the U.S. nuclear arsenal will cost $946 billion in the next decade. The new Sentinel ICBM program alone is already 81% over budget. The National Nuclear Security Administration is juggling seven modernization programs at once. Adding a numerical arms race on top of this modernization effort would be financially devastating.

Nuclear deterrence isn’t just about who has the most bombs. A more effective, modernized force protects America better than just adding more warheads. Every extra dollar spent chasing parity with Russia is a dollar not spent on conventional military priorities like new ships, drones or other tech.

Meanwhile, Russia has structural advantages in this competition that Americans should not dismiss. Russian factories can crank out ammo, rockets and tanks much faster than the U.S. or other NATO countries.

In America, defense contractors chase shareholder returns instead of building capacity. Lobbyists and donors pressure Congress into pouring money into the Pentagon, while diverting profits to stock buybacks rather than investing in the industrial base America needs.

A numerical arms race would play to Russian strengths, not American ones. The question is whether American policymakers see this and choose modernization and pragmatic diplomacy, or if they give in to worst-case fears and start ramping up the arms buildup.

Americans understand the risks of a reckless arms race. A January 2026 poll found that 91% of Americans believe the U.S. should negotiate a new agreement with Russia to keep or reduce nuclear limits. This is not a partisan issue: Eighty-five percent of Donald Trump voters said the president should accept Russia’s offer to stick to New START’s limits for at least another year.

Nearly three-quarters of all voters, including 61% of Republicans, believe removing all nuclear limits would make America less secure.

What can be done now?

Despite sharp disagreements over Ukraine and other issues, there are several options for the U.S. and Russia to support strategic stability.

President Trump and Russian President Vladimir Putin could both make a public promise to stick to New START’s main limits for a fixed period while they work out something more lasting. Such a pledge wouldn’t bring inspections back overnight, but it would send a clear message that both sides do not want to start an arms race.

Washington and Moscow should urgently bring back some basic transparency and risk-reduction steps. This means notifying each other before major nuclear drills or missile tests, sharing data on strategic forces and keeping crisis hotlines open between their militaries. Virtual verification technologies developed during the COVID pandemic could supplement on-site inspections if political obstacles prevent their immediate resumption. None of this relies on trust. It’s just common sense: Nobody wants an accidental disaster.

The U.S. should start talks for a new agreement focused initially on deployed strategic warheads and launchers. This new deal could cover emerging technologies, like hypersonic weapons and advanced missile defenses. If they can agree to put a lid on the most dangerous systems, it will make future negotiations (maybe even with other nuclear-armed states) a whole lot easier than just leaving things up in the air.

President Trump has wisely recognized that “tremendous amounts of money are being spent on nuclear” and that “the destructive capability is something that we don’t even want to talk about.” He is right. The question now is whether his administration will translate that sentiment into policy action.