Russia has vetoed a resolution at the UN Security Council calling on all countries to prevent an arms race in outer space.
The draft resolution, put forward by the US and Japan, sought to reaffirm a principle already set out in the 1967 Outer Space Treaty.
The US has warned that Russia is believed to be developing a space-based, anti-satellite nuclear weapon.
Russia said it was "firmly committed" to the existing treaty.
The draft, put forward on Wednesday, called on "all States, in particular those with major space capabilities, to contribute actively to the objective of the peaceful use of outer space and of the prevention of an arms race in outer space."
It also called on countries to uphold the Outer Space Treaty, under which all parties agreed "not to place in orbit around the Earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction".
Of the council's 15 members, 13 voted in favour, while Russia - one of five permanent members with a veto - voted against and China abstained.
Linda Thomas-Greenfield, the US ambassador to the UN, called the move "baffling".
"Russia has vetoed a straightforward resolution that affirms a legally binding obligation," she said. "President Putin himself has said publicly that Russia has no intention of deploying nuclear weapons in space.
"So today's veto begs the question, why? Why, if you are following the rules, would you not support a resolution that reaffirms them? What could you possibly be hiding?"
In February, White House spokesperson John Kirby said Russia was developing a "troubling" new anti-satellite weapon, though added that the weapon was not yet operational.
The weapon was space-based and armed with a nuclear weapon to target satellites, the BBC's US partner CBS News reported.
Russian President Vladimir Putin said in response that Moscow was "categorically against" the use of nuclear weapons in space.
More than any of its potential global adversaries, the US depends on satellite communications for everything from military operations and surveillance to civilian uses like GPS systems and financial transactions.
On Wednesday, US national security adviser Jake Sullivan reiterated that the US assessed that "Russia is developing a new satellite carrying a nuclear device".
India’s economy will become carbon neutral by the year 2070, the country’s prime minster has announced at the COP26 climate crisis summit in Glasgow. The target date is two decades beyond what scientists say is needed to avert catastrophic climate impacts. India is the last of the world’s major carbon polluters to announce a net-zero target, with China saying it would reach that goal in 2060, and the United States and the European Union aiming for 2050.
China's carbon emissions are vast and growing, dwarfing those of other countries. Experts agree that without big reductions in China's emissions, the world cannot win the fight against climate change. In 2020, China's President Xi Jinping said his country would aim for its emissions to reach their highest point before 2030 and for carbon neutrality before 2060. His statement has now been confirmed as China's official position ahead of the COP26 global climate summit in Glasgow. But China has not said exactly how these goals will be achieved.
China's carbon emissions are vast and growing, dwarfing those of other countries. Experts agree that without big reductions in China's emissions, the world cannot win the fight against climate change. In 2020, China's President Xi Jinping said his country would aim for its emissions to reach their highest point before 2030 and for carbon neutrality before 2060. His statement has now been confirmed as China's official position ahead of the COP26 global climate summit in Glasgow. But China has not said exactly how these goals will be achieved.
A crucial U.N. conference heard calls on its first day for the world's major economies to keep their promises of financial help to address the climate crisis, while big polluters India and Brazil made new commitments to cut emissions. World leaders, environmental experts and activists all pleaded for decisive action to halt the global warming which threatens the future of the planet at the start of the two-week COP26 summit in the Scottish city of Glasgow on Monday. The task facing negotiators was made even more daunting by the failure of the Group of 20 major industrial nations to agree ambitious new commitments at the weekend.