With New Start, signed for a period of ten years, the two countries promised to reduce their number of long-range nuclear weapons; In addition, the text provided additional details on the different types of launchers.

The treaty limited the nuclear arsenal to 700 intercontinental ballistic missiles (ICBMs) and strategic sea-to-surface ballistic missiles (SLBMs), 1,550 nuclear warheads, and 800 launch vehicles (deployed and undeployed).

These objectives were achieved on 5 February 2018.

The text also included effective mechanisms for inspecting and verifying the compliance of the actions of both parties under the terms of the treaty.

It provided for two annual exchanges, as well as a continuous system of mutual notifications regarding the movement of strategic nuclear forces, which took place almost daily.

Both sides agreed to reciprocal on-site inspection of missiles, warheads, and launchers covered by the treaty, which provided each side with valuable information about the other's nuclear deployments.

Finally, the agreement established a bilateral advisory commission and clear procedures for the resolution of issues or disputes.

Limitations of the agreement
 

At the time, the treaty was criticized for the modest nature of the reductions it imposed and for the limited scope of the types of nuclear weapons it covered.

But his main weakness was the political price Obama had paid to get it ratified by the US Senate.

In order to garner sufficient support from Republicans, the Democratic president agreed to a long-term, more than $2 trillion program to renew and modernize the US nuclear arsenal, as well as nuclear weapons production and maintenance facilities and programs.

As a result, with New Start, the United States ensured that it continued to have a substantial and constantly modernized nuclear arsenal.

The prospects of total disarmament were fading.

As the expiry of the treaty, which expired in 2021, approached, Russia had proposed to extend its validity by five years, as allowed by the provisions of the text.

Donald Trump, who was then serving his first presidential term, refused to follow through.

After his victory in the 2020 presidential election, Joe Biden finally agreed to the extension of the treaty on February 3, 2021, just two days before it expired. However, no further extension is provided for in the Treaty.

In February 2023, Russia suspended the application of some key aspects of the agreement, including the exchange of data on stocks and on-site inspections. However, it has not formally withdrawn from the treaty and has pledged to continue to respect numerical limits on warheads, missiles and launchers.

And now?
 

In September 2025, as the treaty neared its expiry, Vladimir Putin signalled that he was ready to continue to respect the limits set for another year, provided that the United States did the same.

Apart from an off-the-cuff remark by Donald Trump – "It seems to me to be a good idea" – no official response has been given by Washington to this Russian proposal.

Trump has also complicated the situation by demanding that any future negotiations on nuclear arms control include China. However, Beijing has always refused to participate.

Moreover, there is no precedent for trilateral negotiations on nuclear disarmament or control, which would be lengthy and complex. And while China's arsenal is expanding, it now accounts for only 12% of that of the United States and less than 11% of that of Russia.

The New START treaty now seems doomed to expire without any agreement being reached to maintain its limits until a replacement treaty is negotiated.

This means that Russia and the United States could increase the number of their deployed warheads by 60% and 110% respectively in the space of a few months.

Both have the ability to load more warheads onto their missiles and bombers than is currently the case. They also keep large stocks of warheads in reserve or intended for dismantling, but still intact.

If they took such steps, the two countries could nearly double their deployed strategic nuclear arsenals.

The end of the data exchange, verification and notification processes would lead to great uncertainty and mutual distrust. This in turn could lead to a further strengthening of the two countries' already colossal military capabilities.

A worrying warning
 

Perhaps the most worrying aspect of this development is the fact that nuclear disarmament is now moribund.

No negotiations on disarmament or even on nuclear risk limitation are currently under way. None are planned.

At the very least, after the New START treaty expires this week, Russia and the United States are expected to agree to respect its limits until they negotiate further cuts.

And fifty-six years after having made a commitment to disarmament under the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), the two powers should work towards the establishment of an agreement between all the nuclear-weapon States in order to eliminate their arsenals.

But Russia, the United States and the other nuclear powers are now moving in the opposite direction.

Since his return to power, Donald Trump has multiplied actions, from bombing Iran to arresting Venezuelan leader Nicolas Maduro, that show his contempt for international law and treaties. They also confirm his desire to use all levers of power to assert American supremacy.

Vladimir Putin, for his part, has resorted to an IRBM, the famous Orechnik, against Ukraine, multiplied threats of the use of nuclear weapons against Kiev and the West, and opted for an unprecedented and extremely dangerous approach to Ukrainian nuclear power plants, around which fighting takes place regularly and which now operate in a very degraded environment, This raises immense risks.

All of this bodes ill for nuclear disarmament and, beyond that, for reducing the possibility of nuclear war.

* Tilman Ruff, Honorary Principal Fellow, School of Population and Global Health, The University of Melbourne, he is affiliated with the International Association of Physicians for the Prevention of Nuclear War and, the International Campaign to Abolish Nuclear Weapons.

*This article is republished from The Conversation under a Creative Commons license.