By Guy Faulconbridge
MOSCOW (Reuters) -U.S. President Donald Trump on Sunday said Russian President Vladimir Putin's offer to voluntarily maintain limits for a year on deployed strategic nuclear weapons "sounds like a good idea".
What would it mean for nuclear arms control and what are the main issues ahead?
WHAT DID PUTIN OFFER?
Having long declined to address arms control in isolation, Putin in September offered to voluntarily maintain for one year the limits on deployed strategic nuclear weapons set out in the New START Treaty, which expires on Feb. 5, 2026.
New START, the last remaining Russian-U.S. arms control treaty, was signed by then-presidents Barack Obama and Dmitry Medvedev in 2010 and came into force in 2011. It was extended for five years in 2021 by Putin and then-U.S. president Joe Biden.
WHAT IS A "STRATEGIC" WEAPON?
Strategic weapons are usually long-range and designed to influence the outcome of a war rather than merely a battle, by destroying centres of power, command and control facilities or nationally critical infrastructure.
WHY DOES IT MATTER?
Russia and the U.S. together have about 87% of the global inventory of nuclear weapons - enough to destroy the world many times over. Russia has 5,459 nuclear warheads while the United States has 5,177, according to the Federation of American Scientists (FAS).
Their arms control treaties were born out of fear of nuclear war after the 1962 Cuban Missile Crisis. Greater transparency about the opponent's arsenal was intended to reduce the scope for misunderstanding and slow the arms race.
Now, with all major nuclear powers seeking to modernise arsenals, and Russia and the West at strategic loggerheads for over a decade, not least over Moscow's war in Ukraine, the treaties have almost all crumbled away. Each side blames the other.
WHAT HAPPENS NEXT?
Putin said it was unclear what would happen in the future if a one-year extension was signed. He said further voluntary limits would depend on U.S. actions.
WHAT ARE THE ISSUES?
* Putin said Washington's "preparations for deploying interceptors in space" could undermine efforts to maintain the status quo. Trump said in May he had selected a design for the $175-billion Golden Dome project, which would create a network of perhaps hundreds of satellites to detect, track and potentially intercept incoming missiles.
* Russia and the U.S. both have new weapons systems that the other side says are essentially strategic. Putin said the U.S. considers the "Oreshnik" intermediate-range ballistic missile as a strategic weapon. Russia also has the Kinzhal manoeuvrable ballistic missile and the Avangard nuclear-capable, hypersonic boost-glide vehicle.
* Tactical nuclear weapons: These are usually short-range, designed for use on the battlefield, and generally left out of nuclear weapons treaties. Russia has about 1,477 non-strategic warheads while the United States has about 200, according to the FAS. Putin has specifically mentioned tactical nuclear weapons as an issue.
* Submarines: The United States has more strategic nuclear submarines than Russia.
* China: Putin has said the U.S. wants Moscow to get its ally China involved in arms control, though Moscow says it is up to Beijing and that, if China is involved, Britain and France should be too. The FAS estimates China has about 600 nuclear warheads and rising, but Beijing says it does not want to enter negotiations with countries that have much bigger arsenals.
NUCLEAR TESTING
Russia has repeatedly raised concerns in public about a possible resumption of nuclear testing. During Trump's first term as president, from 2017-2021, his administration discussed whether or not to conduct the first U.S. nuclear test since 1992, the Washington Post reported in 2020.
Putin said on October 2 that Russia would carry out a nuclear test if another nuclear power did so, saying it had seen signs that an unnamed country was making such preparations: "We see it, we know it and, if it happens, we will do the same."
(Reporting by Guy Faulconbridge; Editing by Kevin Liffey)
