The last remaining treaty limiting deployable nuclear weapons between the United States and Russia expired on Thursday, ending decades of bilateral arms control between the world’s two largest nuclear powers.
The New START treaty, signed in 2010, capped deployed strategic nuclear warheads at 1,550 for each country. It also established inspection regimes and notification requirements designed to ensure compliance.
Russia halted inspections and notifications during its war in Ukraine, but the US State Department said last month that Moscow is not believed to have significantly exceeded the treaty’s limits.
Former US president Joe Biden extended the agreement in 2021 for five years, the final extension permitted under the treaty. No further renewal was possible.
In January, President Donald Trump suggested he could allow the treaty to lapse, telling The New York Times: “If it expires, it expires.” A White House official later told CBS News that the president would outline his approach to nuclear arms control “on his own timeline”.
Trump has indicated support for maintaining limits on nuclear weapons while pushing for China to be included in any future agreement.
Secretary of State Marco Rubio said on Wednesday that reaching a new deal without China would be “impossible”, citing Beijing’s expanding arsenal. The Pentagon estimates China will possess more than 1,000 nuclear warheads by 2035, up from around 200 in 2019.
The expired treaty applied only to Washington and Moscow, which currently possess about 4,300 and 3,700 nuclear warheads respectively, according to the Federation of American Scientists.
Russian president Vladimir Putin suggested in September that both countries should continue observing the treaty’s limits for a year without signing a new agreement. Rose Gottemoeller, a former US under secretary of state for arms control, told senators this was a workable option.
“It should be Donald Trump who gets to be the president of nuclear peace in this case, not Vladimir Putin,” Gottemoeller told the Senate Armed Services Committee. She said a temporary continuation of the limits could help restore strategic stability and keep negotiations alive.
Others disagreed. Retired Admiral Charles Richard, former head of US Strategic Command, and Tim Morrison, a former White House national security official during Trump’s first term, argued the treaty failed to address key threats.
All three officials agreed the agreement was flawed, particularly because it excluded China and did not limit non-strategic or tactical nuclear weapons. Gottemoeller said, however, that it was preferable to having no constraints at all.
She warned that the US should not be forced to manage China’s nuclear expansion while also facing a rapid Russian increase in deployed weapons.
With the treaty now expired, officials expressed concern that other countries may reconsider their own nuclear ambitions.
“I don’t think you can understate the risk of proliferation,” Morrison said.
Morrison also highlighted the ageing US nuclear arsenal, warning that by 2035 all US nuclear warheads and bombs will be well beyond their original design lives.
He argued that effective deterrence depends on sustained investment and the ability to respond decisively to treaty violations.
The officials also stressed the need to strengthen the US defence industrial base, particularly for building Columbia-class submarines, which will form the backbone of the sea-based nuclear force.
“The numbers are insufficient across the triad,” Richard said, referring to the air, land and sea components of US nuclear forces. He added that additional capabilities may be required beyond existing modernisation plans.
