White House says weapon is not yet operational and poses no immediate threat but puts astronauts at risk.

National security spokesman John Kirby said US intelligence officials had information that Russia had developed the technology but that the weapon was not currently operational.

He said US officials were analysing the information they had and consulting with allies in Europe.

“This is not an active capability that’s been deployed, and though Russia’s pursuit of this particular capability is troubling, there is no immediate threat to anyone’s safety,” Kirby said on Thursday.

He confirmed the weapon was “space-based” but would not comment on reports in US media that it was either nuclear-capable or nuclear-powered.

“We’re not talking about a weapon that can be used to attack human beings or cause physical destruction here on Earth,” he said.

Moscow downplayed the US claims, describing them as a “malicious fabrication” that were a White House ploy to try and secure the passage of a multibillion-dollar Ukrainian aid package through a resistant Republican-led House of Representatives.

“It’s obvious that Washington is trying to force Congress to vote on the aid bill by hook or by crook,” Kremlin spokesperson Dmitry Peskov said in remarks carried by Russian news agencies. “Let’s see what ruse the White House will use.”

The US and the United Kingdom previously alleged Russia had tested a space weapon in 2020. On that occasion, Moscow said the claims were “propaganda“.

Kirby said the latest weapon could pose a lethal risk to astronauts in low orbit, along with potentially disrupting vital military and civilian satellites.

It would also breach the 1967 Outer Space Treaty, which prohibits the deployment of “nuclear weapons or any other kinds of weapons of mass destruction” into orbit or to “station weapons in outer space in any other manner”. More than 130 countries have signed the agreement, including Russia and the US.

Experts said the US does not have the capability to counter such a weapon.

US President Joe Biden had been kept informed and had requested direct diplomatic engagement with Moscow over the weapon.

The threat came to light after Mike Turner, chairman of the House of Representatives Intelligence Committee, issued an unusual warning about a “serious national security threat” and called on Biden to “declassify all information relating to this threat”.

On Thursday, another Republican House member, Andy Ogles, urged House Speaker Mike Johnson to investigate the impact Turner’s action may have had on foreign and domestic policy, asking whether he should remain chairman.

White House national security adviser Jake Sullivan also briefed lawmakers.

After the meeting, Turner said Sullivan had discussed the administration’s options in addressing the potential threat.

“I think the bottom line is that we all came away with a very strong impression that the administration is taking this very seriously and that the administration has a plan in place,” he said. “We look forward to supporting them as they go to implement it.”

Johnson, who also attended the briefing, said it was  “informative” and that the White House will remain in close contact with lawmakers about the matter.

“It is a very serious matter. It does involve Russia,” Johnson told reporters, adding that the administration and Congress would stay in close contact. “And it will be dealt with.”

The US sees Russia and China as its biggest nation-state competitors and says both are developing a range of new weapons systems, including nuclear, cyber and space capabilities.