Last US-Russia nuclear treaty expires – what’s at stake?

US President Barack Obama (left) and his Russian counterpart Dmitry Medvedev during the signing of the New START treaty on Thursday, 8 April 2010, in Prague. Keystone

The last remaining nuclear arms pact between Russia and the United States – the New START treaty – expired on February 5, removing any caps on the two largest atomic arsenals for the first time in over 50 years and raising the risk of a new arms race.

What is the New START treaty?

The New START treaty is a bilateral agreement between Washington and Moscow. Signed in 2010 by presidents Barack Obama and Dmitry Medvedev, it has been in force since 2011 and limits the long-range nuclear arsenals of the US and Russia.

The agreement caps each country at 1,550 “strategically deployed” nuclear warheads. It does not cover “tactical” weapons with generally lower power and range, such as those that Vladimir Putin refused to use in Ukraine. The term “deployed” refers to a warhead mounted on either a missile or a bomber. The treaty limits their number to 700 each, while launchers are limited to 800.

The treaty is part of a series of agreements – such as the SALT, START and SORT treaties – which aimed to reduce the total nuclear arsenal of the US and Russia, which exceeded 60,000 warheads at the end of the Cold War. The treaty was initially due to expire in 2021, but was extended for an additional five years until February 4, 2026. No other extension is possible under the terms of the agreement.

What are the consequences of the termination of the treaty?

New START is the sole accord governing the nuclear arsenals of Russia and the US – the two powers that together hold about 90% of the world’s 12,000 nuclear weapons. The parties opposed to nuclear weapons fear that the termination of the treaty will open the door to an arms race between the two countries. This will be the first time since 1972 that no agreement of this kind has been reached between them.

“It is disturbing to see that this treaty will expire without any agreement on its replacement,” said Alicia Sanders-Zakre, Head of Political Affairs at the International Campaign for the Abolition of Nuclear Weapons (ICAN), a Geneva-based NGO coalition. “A new nuclear arms race between the US and Russia would only add to the level of risk that is already unacceptable today,” she added, calling for a total disarmament of nuclear weapons.

On January 27, the Doomsday ClockExternal link – created by scientists to symbolically represent how close humanity is to destroying the world – was updated and set at 85 seconds to midnight, the closest the clock has ever been to midnight in its history, representing a nuclear apocalypse; last year it was 89 seconds to midnight. It reflects the danger perceived by a panel of experts, who also highlighted the involvement of nuclear weapons in conflicts such as in Ukraine and the Middle East, and the modernisation of nuclear arsenals.

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Was the New START treaty respected?

Partially. The agreement allowed for a certain degree of transparency between the two powers and a mutual verification mechanism that included on-site inspections and the exchange of data on each country’s arsenals. In 2020, inspections were suspended by a joint agreement between Washington and Moscow due to the Covid-19 pandemic.

“The Americans were ready to resume the visits. But relations have deteriorated because of the invasion of Ukraine by Russia and the sanctions that Washington subsequently imposed on Moscow,” explained Marc Finaud, a researcher at the Geneva Centre for Security Policy (GCSP) and a nuclear disarmament expert. “In February 2023, the Russians decided to suspend the application of certain aspects of the treaty, while continuing to respect the ceilings.”

Although the exchange of data and the mutual visits have never resumed, there are no indications that either side has exceeded the maximum limits.

Can New START be renewed?

The treaty cannot be extended again. But in September last year Putin proposed to voluntarily respect the ceilings for an additional year, a proposal to which US President Donald Trump has not officially replied.

In theory, a new agreement could be negotiated, but it is not clear that the conditions have been met. “Between negotiations on Ukraine, threats against Greenland and now Iran, the climate is clearly not conducive to the resumption of negotiations, in any case not in the short term,” said Finaud, who is also vice-president of the French Nuclear Disarmament Initiative (IDN). “It is therefore very difficult to predict what will happen.”

Asked by The New York TimesExternal link at the beginning of the year about the outcome of the treaty, Trump declared: “If it expires, it expires. We’ll do a better agreement.” He has suggested that he wants a new treaty that includes China, but the latter is against it because its arsenal – even if it is growing – represents only 10% of that of Russia and the US. On the other hand, Moscow believes that France and the UK, Washington’s allies in NATO, should be included, which they also refuse.

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What are the other main international nuclear treaties?

The US, Russia and three other nuclear powers remain parties to the 1968 Treaty on the Non-Proliferation of Nuclear Weapons (NPT), which obliges states to work towards nuclear disarmament.

“It is very worrying that New START is being cancelled. But that doesn’t mean that the US and Russia are no longer subject to constraints; they are via the NPT, which has no expiry date,” Sanders-Zakre pointed out.

However, the NPT does not contain any specific objectives, particularly regarding the reduction of nuclear arsenals. This is why the international community decided in 2017 to supplement it by creating the Treaty on the Prohibition of Nuclear Weapons (TPNW).

The treaty, which has been signed by around 100 countries, bans the development, testing, production, possession, destruction and use of nuclear weapons, as well as the threat of their use. It should also make it possible to exert pressure on those states that have nuclear weapons, but at present neither the nuclear powers nor their main allies have adopted it.

“As long as there is just one nuclear weapon left, the risk still exists that it could be used. The only guarantee is therefore to eliminate all of them, and that is why TPNW is so important,” said Sanders-Zakre.

Edited by Virginie Mangin/adapted from French with AI/sb