Russia has vetoed a resolution at the UN Security Council calling on all countries to prevent an arms race in space.
The draft resolution presented by the United States and Japan sought to reaffirm a principle already established in the 1967 Outer Space Treaty.
The US has warned that Russia is likely developing a space-based anti-satellite nuclear weapon.
Russia said it was “firmly committed” to the existing treaty.
The draft, presented on Wednesday, called on “all states, especially those with large space capabilities, to actively contribute to the goal of the peaceful use of outer space and the prevention of an arms race in outer space.”
It also called on countries to comply with the Outer Space Treaty, in which all parties agreed “not to place into Earth orbit any objects carrying nuclear weapons or other types of weapons of mass destruction.”
Of the 15 council members, 13 voted in favor, while Russia – one of five permanent members with veto power – voted against and China abstained.
Linda Thomas-Greenfield, the U.S. ambassador to the United Nations, called the move “confusing.”
“Russia vetoed a simple resolution that reaffirms a legally binding commitment,” she said. “President Putin himself has publicly stated that Russia has no intention of placing nuclear weapons in space.
“So today’s veto begs the question: Why? If you play by the rules, why wouldn’t you support a resolution that reinforces them? What could you possibly be hiding?”
In February, White House spokesman John Kirby said Russia was developing a “troubling” new anti-satellite weapon, but added that the weapon was not yet operational.
The weapon was stationed in space and equipped with a nuclear weapon to attack satellites, the BBC’s US partner CBS News reported.
Russian President Vladimir Putin responded by saying Moscow was “categorically opposed” to the use of nuclear weapons in space.
More than any of its potential global adversaries, the United States depends on satellite communications for everything from military operations and surveillance to civilian applications such as GPS systems and financial transactions.
On Wednesday, US national security adviser Jake Sullivan reiterated that the US believes “Russia is developing a new satellite that will carry a nuclear bomb.”
Details of the intelligence behind the claim have not been released.
Russian Foreign Minister Sergei Lavrov said: “Russia is firmly committed to its international legal obligations, including the 1967 Outer Space Treaty.”
Russia’s UN envoy Vasily Nebenzia called the US-Japanese resolution a “cynical ploy” with “hidden motives”.
The UN Security Council consists of five permanent members – the US, Britain, France, China and Russia – each of which has veto power, and ten seats that rotate between other UN member states.