The US has observed Russian naval vessels preparing for a possible test of a new nuclear torpedo in recent weeks, a senior US official with direct knowledge told CNN.   

  Among the ships participating in the preparations was the Belgorod, a cruise missile submarine modified for special operations that can launch unmanned underwater vehicles, including the Poseidon torpedo.   

  Over the past week, vessels have been seen leaving the testing area in the Arctic Sea and returning to port without conducting a test.  The US believes the Russians may have experienced technical difficulties.   

  “This can be seen as part of the bigger picture and Russia’s recent military practice of sending ill-trained and ill-equipped soldiers into Ukraine,” a Western diplomat told CNN.  “The Russian military industry is going through difficult times, and we can also see that Western sanctions on high-tech military products are having an effect and should be continued.”   

  U.S. officials have said Russia could attempt to test the torpedo again, but note that the waters in the test area will soon begin to freeze, limiting the window for operations.   

  A test of the torpedo would likely further inflame tensions with the US at a time when Washington and its allies have been watching closely for any signs that Russia may be preparing to use nuclear weapons in the war in Ukraine.  The US has also paid close attention to any possible tests of the Poseidon torpedo.   

  The Poseidon torpedo is a nuclear-powered unmanned underwater vehicle capable of carrying conventional and nuclear munitions.  Its nuclear propulsion system gives the Poseidon virtually unlimited range.   

  The US does not believe any test would result in the detonation of a nuclear device.  Any potential danger would come from a malfunction of the nuclear propulsion system, which could create radioactivity hazards.   

  President Vladimir Putin first announced the existence of the Poseidon system during his 2018 State of the Nation address, touting it as an “innovative” new weapon.   

  “The nuclear power plant is unique for its small size, while offering an amazing power-to-weight ratio.  It is a hundred times smaller than the units that power modern submarines, but it is even more powerful and can go into combat mode, i.e. reach maximum capacity, 200 times faster,” Putin said at the time.   

  The Belgorod is the longest submarine in the ocean today and was delivered to the Russian Navy in June.   

  At more than 608 feet, it is even longer than the US Navy’s Ohio-class ballistic and guided-missile submarines, which reach 569 feet.   

  The Belgorod was launched in 2019 and was expected to be delivered to the Russian Navy in 2020 after tests and trials, but these were delayed due to the coronavirus pandemic, Russian state news agency TASS reported.  No timetable was given for the submarine’s first deployment.   

  TASS previously reported that the submarine will carry the under-development Poseidon nuclear-capable torpedoes, which are designed to be launched from hundreds of miles away and sneak past coastal defenses by traveling along the seabed.   

  In November 2020, Christopher Ford, then-Assistant Secretary of State for International Security and Non-Proliferation, said that the Posidonias were designed to “inundate US coastal cities with radioactive tsunamis”.   

  A US Congressional Research Service (CRS) report in April said the Neptunes are intended as retaliatory weapons, designed to strike back at an enemy after a nuclear strike on Russia.   

  According to the CRS report, the Belgorod could carry up to eight Poseidons, although some weapons experts say its payload is more likely to be six torpedoes.