The secretive Russian satellite in space that U.S. officials believe is connected to a nuclear anti-satellite weapon program has appeared to be spinning uncontrollably, suggesting it may no longer be functioning in what could be a setback for Moscow's space weapon efforts, according to U.S. analysts.

U.S. officials assess Cosmos 2553's purpose, though not itself a weapon, is to aid Russia's development of a nuclear anti-satellite weapon. Russia has denied it is developing such a weapon and says Cosmos 2553 is for research purposes.