FEATURE | Trump rejects Russian proposal to extend nuclear weapons deployment caps

Ukraine, which has been at war with Russia since Moscow's 2022 invasion, said the treaty's expiry was a consequence of Russian efforts to achieve the "fragmentation of the global security architecture" and called it, "another tool for nuclear blackmail to undermine international support for Ukraine."

Strategic nuclear weapons are the long-range systems that each side would use to strike the other's capital, military and industrial centres in the event of a nuclear war. They differ from so-called tactical nuclear weapons that have a lower yield and are designed for limited strikes or battlefield use.

If left unconstrained by any agreement, Russia and the US could each, within a couple of years, deploy hundreds more warheads beyond the New START limit of 1,550, experts say.

"Transparency and predictability are among the more intangible benefits of arms control and underpin deterrence and strategic stability," said Karim Haggag, director of the Stockholm International Peace Research Institute.

(Reporting by Dmitry Antonov in Moscow and Mark Trevelyan in London; additional reporting by Mei Mei Chu in Beijing, Shubham Kalia in Bengaluru, Andrea Shalal, Jonathan Landay and David Brunnstrom in Washington. Editing by Timothy Heritage and Mark Porter)