What is New START?

New START is a 10-year nuclear arms reduction treaty between Russia and the US, running on an additional five-year extension. Signed in April 2010, it came into force on February 5, 2011 upon ratification by both parties.
The treaty limits each country to no more than 1,550 deployed nuclear warheads (down nearly two-thirds from the original 1991 START I treaty) and 700 deployed missiles and bombers. Crucially, it also allows for satellite and remote monitoring, as well as 18 on-site inspections per year to verify limits.
Significantly, the treaty does not cover weapons that fly on a ballistic trajectory for less than 50% of their flight, as is the case for most hypersonic gliders and missiles. This should be rectified and updated in any future agreement.

New START under the first Trump Administration

President Trump didn’t show much interest in extending New START for the first three years of his Administration. In his first call with the Kremlin, it was reported that he denounced the agreement as one of several bad deals negotiated by the Obama Administration. In part, this was because the treaty only addressed strategic nuclear weapons, leaving Russia’s tactical arsenal – far greater than that of the US (Moscow has ~1,558 non-strategic warheads compared with Washington’s 200) – untouched. As part of the negotiations over extending New START, the Trump Administration hoped to force Russia to agree to a freeze in its overall number of nuclear warheads.
However, in April 2019, CNN reported that President Trump was aiming not for a simple extension of New START, but a new treaty with both Russia and China that would include non-strategic weapons. Yet the scale of those ambitions meant some observers (though surely not correct) feared the Administration was using China as a “poison pill” to sabotage talks and exit what it regarded as a constraining and outdated nuclear pact.
Beijing repeatedly made it clear it had no intention of joining a nuclear pact, pointing to its much smaller arsenal compared to that of Washington and Moscow, which collectively comprise 90% of the global nuclear weapons stockpile. Nonetheless, the Trump Administration remained fixated on bringing China into a new trilateral arms deal until the autumn of 2020, alarmed by its rapid expansion of warheads. (Between 2014 and 2024, the estimated number of China’s warheads doubled from roughly 250 to 500, growing by more than 20% in 2023–24 alone. By mid-2024, the Pentagon had revised its estimate upwards to 600 and warned Beijing would likely have 1,000 nuclear warheads by 2030.)

On October 2, the US floated the idea of a one-year extension of New START (without Chinese participation) on the condition that all warhead levels be frozen in tandem. After some back-and-forth, Russia publicly conceded to this but vetoed American calls for a beefed-up verification regime. By the following month, it became clear this was an insuperable sticking point. Talks stalled and stopped with the election of President Biden.

New START under the Biden Administration

Shortly after his inauguration, President Biden agreed to a five-year extension of New START without imposing any further conditions. But things took a rapid turn for the worse after Putin’s invasion of Ukraine.
In August 2022, Moscow declared it was suspending inspections of its military sites (on hold since the start of the pandemic), alleging that Russian inspectors faced one-sided restrictions due to tougher visa requirements in transit countries and allies closing their airspace to Russian aircrafts. Three months later, Russia unilaterally postponed a meeting due to be held in Cairo to discuss resuming mutual inspections, explicitly linking the decision to Washington’s support for Kyiv.
On February 21, 2023 Putin suspended Russia’s participation in New START, though he insisted this did not amount to a full withdrawal and could be reversed if the US “demonstrates the political will and takes honest efforts towards general de-escalation”.

Despite some promising signals in mid-2023, a few months later Russian officials began indicating that the nuclear issue could not be divorced from the Ukraine conflict. This was explicitly confirmed by Foreign Minister Lavrov in January 2024, and reiterated by senior Russian security official Dmitry Medvedev in a Telegram update.