New START Expires, Leaving U.S. and Russia Without Binding Caps on Strategic Nuclear Arms

As midnight passed in Washington and Moscow on Feb. 5, there were no sirens, no televised addresses, no dramatic countdown. Yet with the quiet expiration of the New START treaty, the United States and Russia slipped into a new nuclear era: for the first time in more than half a century, there is no legally binding limit on the size of their strategic arsenals.

United Nations Secretary-General António Guterres marked the moment in unusually stark terms. In a statement issued that day, he called the treaty’s end “a grave moment for international peace and security” and urged both governments to “act urgently to agree a new framework for nuclear arms control.”

New START — formally the Treaty on Measures for the Further Reduction and Limitation of Strategic Offensive Arms — had been the last remaining bilateral agreement capping the deployed long-range nuclear weapons of the world’s two largest nuclear powers. Its demise leaves Washington and Moscow legally free to increase the number of warheads and delivery systems they field, without inspections or data exchanges to reassure the other side.

Officials in both capitals insist they do not intend to launch a rapid arms buildup. Russian Foreign Minister Sergey Lavrov told lawmakers that Moscow would continue to observe the treaty’s numerical limits “as long as” the United States does so, and Kremlin spokesman Dmitry Peskov said Russia was “in no rush” to expand its deployed forces. U.S. officials have not announced any immediate changes to U.S. warhead levels.

The new landscape, however, is one in which restraint is voluntary, unverifiable and revocable at any time.

The last guardrails removed

New START was signed in Prague on April 8, 2010, by President Barack Obama and then-Russian President Dmitry Medvedev and entered into force on Feb. 5, 2011. The treaty limited each side to 1,550 deployed strategic nuclear warheads, 700 deployed intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs) and nuclear-capable heavy bombers, and 800 deployed and nondeployed missile launchers and bombers.

Beyond the headline numbers, the agreement built a dense framework of transparency. Each country was allowed up to 18 short-notice inspections per year at the other’s nuclear bases and support facilities. Twice a year, they were required to exchange detailed data on the locations and status of their strategic forces and to issue thousands of notifications annually about movements, conversions and eliminations of missiles and launchers. A Bilateral Consultative Commission met regularly to resolve technical disputes.

Arms control specialists widely credited that system with providing predictability and reducing the risk of miscalculation. By February 2018, both sides had formally met New START’s limits. The treaty was extended in early 2021 for five years — the maximum allowed — pushing its expiration date to Feb. 5, 2026.

Much of its verification machinery, however, had already fallen dormant. In February 2023, Russian President Vladimir Putin announced that Russia was “suspending” its participation, citing what he called “hostile” U.S. and NATO actions over the war in Ukraine and objecting to inspection activities on Russian territory. Moscow said it would continue to respect the numerical ceilings, but inspections and routine data exchanges stopped. The United States responded by halting its own data sharing.

The treaty itself remained in force until this year. Its expiration closes a chapter that began with the first Strategic Arms Limitation Talks in the late 1960s and yielded a series of accords: SALT I, the Anti-Ballistic Missile Treaty, the Intermediate-Range Nuclear Forces (INF) Treaty, START I and others. Most have been abandoned or lapsed over the last two decades.

“With the end of New START, there are now no enforceable, verifiable limits on the world’s two largest nuclear arsenals,” said one former U.S. negotiator who worked on the treaty, speaking on background. “That hasn’t been true since the earliest days of the arms race.”

Missed chances and hardened positions

The years leading up to New START’s expiration were marked by deepening mistrust and failed diplomacy.

Russia’s 2014 annexation of Crimea and its full-scale invasion of Ukraine in 2022 severely damaged relations with the United States and Europe. Putin paired battlefield moves with frequent references to Russia’s nuclear forces, warning that Western intervention could have “catastrophic consequences.”

Against that backdrop, experts and allied governments urged Washington and Moscow to use the 2021 extension as a bridge to negotiate a successor agreement or a follow-on framework. Those efforts never gained traction.

In September 2025, Putin publicly offered to continue observing New START limits for one year beyond the expiration date, until Feb. 5, 2027, if the United States did the same and refrained from steps such as expanding missile defenses. Arms control advocates welcomed the proposal as a chance to buy time. The offer was not taken up in any formal way.

The current U.S. administration has argued that any new arrangement must be broader and more inclusive than New START, addressing Russia’s new strategic systems and large stockpile of nonstrategic nuclear weapons, as well as the rapid growth of China’s arsenal. President Donald Trump has repeatedly criticized New START as a “badly negotiated” Obama-era deal and said the United States should not “tie its own hands” without bringing Beijing to the table.

China has rejected the idea of joining trilateral negotiations, noting that it possesses far fewer warheads than the United States and Russia and accusing Washington of seeking to constrain its rise.

As the deadline approached this winter, officials described discussions on a possible political understanding to maintain New START’s numerical ceilings even after the treaty expired. So far, no detailed arrangement has been announced. What exists instead is a patchwork of public statements about intended behavior.

Democratic leaders in Congress have faulted the administration for allowing the treaty to lapse. In a joint statement on Feb. 5, Reps. Gregory Meeks of New York, Adam Smith of Washington and Jim Himes of Connecticut said the expiration “represents a serious setback for U.S. and global security” and accused the White House of “squandering the runway” provided by the 2021 extension.

Republican hawks welcomed the end of the accord. Sen. Tom Cotton of Arkansas said in a written statement that New START had “constrained U.S. nuclear forces while Russia cheated and China built up unconstrained” and called for a more expansive U.S. nuclear posture.

Europe watches the gap

European governments, geographically closest to any potential U.S.-Russia confrontation, have reacted with alarm.

France’s Foreign Ministry said the expiry of New START “represents a serious blow to the international arms control architecture” and urged the United States and Russia to “demonstrate responsibility and take concrete measures to preserve strategic stability.” NATO officials have echoed those concerns in public remarks.

The end of the treaty comes on top of the collapse of the INF Treaty, which once banned an entire class of U.S. and Soviet ground-launched missiles with ranges between 500 and 5,500 kilometers, many of them designed for use in Europe. With both agreements gone, some European capitals now face renewed debates about stationing intermediate-range missiles and the role of British and French nuclear forces in a possible “European nuclear umbrella.”

The practical implications may unfold gradually. Both the United States and Russia are already engaged in long-term modernization of their nuclear triads, programs planned years in advance. But analysts say that without treaty limits, each side has greater freedom to adjust force levels upward and to change the way weapons are deployed and alerted, especially if tensions escalate.

The two countries together still account for roughly 85% to 90% of the world’s nuclear warheads, including those in storage or awaiting dismantlement.

Arms control without treaties

The demise of New START also ripples through the broader nonproliferation regime.

The 1968 Nuclear Non-Proliferation Treaty obligates its five recognized nuclear-weapon states, including the United States and Russia, to pursue negotiations on effective measures relating to nuclear disarmament. Many nonnuclear NPT members have long pointed to U.S.-Russian arms reductions as evidence that the bargain is being upheld.

With no U.S.-Russia reduction treaty now in force, diplomats and activists warn that confidence in that bargain could erode further. Support has grown in recent years for the Treaty on the Prohibition of Nuclear Weapons, a separate pact banning nuclear arms outright that the nuclear-armed states have opposed.

The Bulletin of the Atomic Scientists cited the end of New START as one of several reasons for moving its symbolic Doomsday Clock closer to midnight in its 2026 assessment, alongside the war in Ukraine, rising great-power tensions and emerging technologies.

For now, the world’s largest nuclear powers remain where they have been for decades: locked in deterrent postures, each capable of destroying the other many times over. What has changed is the framework around that rivalry. Where there were detailed rules, inspections and structured dialogue, there are now political pledges and intermittent talks.

Whether that proves to be a temporary interlude or the start of an extended period of “nuclear competition without rules” will depend on choices yet to be made in Washington, Moscow and beyond. As Guterres put it in his Feb. 5 statement, “The world cannot afford to sleepwalk into a nuclear arms race that would benefit no one and endanger everyone.”