When Russia conducted a series of secret military satellite launches around the time of its invasion of Ukraine in early 2022, American intelligence officials began delving into the mystery of what, exactly, the Russians were doing.
Later, spy agencies discovered Russia was working on a new kind of space-based weapon that could threaten the thousands of satellites that keep the world connected.
In recent weeks, a new warning has circulated from America’s spy agencies: Another launch may be in the works, and the question is whether Russia plans to use it to put a real nuclear weapon into space — a violation of a half-century old treaty. The agencies are divided on the likelihood that President Vladimir V. Putin would go so far, but nonetheless the intelligence is an urgent concern to the Biden administration.
Even if Russia does place a nuclear weapon in orbit, U.S. officials are in agreement in their assessment that the weapon would not be detonated. Instead, it would lurk as a time bomb in low orbit, a reminder from Mr. Putin that if he was pressed too hard with sanctions, or military opposition to his ambitions in Ukraine or beyond, he could destroy economies without targeting humans on earth.
Despite the uncertainties, Secretary of State Antony J. Blinken raised the possibility of the Russian nuclear move with his Chinese and Indian counterparts on Friday and Saturday on the sidelines of the Munich Security Conference.
Mr. Blinken’s message was blunt: Any nuclear detonation in space would take out not only American satellites but also those in Beijing and New Delhi. Global communications systems would fail, making everything from emergency services to cell phones to the regulation of generators and pumps go awry. Debris from the explosion would scatter throughout low-earth orbit and make navigation difficult if not impossible for everything from Starlink satellites, used for internet communications, to spy satellites.
Since Mr. Putin has made clear his disdain for the United States, Mr. Blinken told them, it was up to the leaders of China and India, President Xi Jinping and Prime Minister Narendra Modi, to talk him down from what could turn into a disaster.
In a statement on Saturday, the State Department said that in his meetings Mr. Blinken had “emphasized that the pursuit of this capability should be a matter of concern.”
“He will continue raising it in additional meetings at the Munich Security Conference,” the statement continued.
It was unclear how much of the intelligence about the 2022 Russian satellite tests, which has not been previously reported, Mr. Blinken shared when he met with China’s foreign minister, Wang Yi, or with India’s, Subrahmanyam Jaishankar.
Some intelligence officials had objected to sharing too much about what the U.S. knows because the details of the Russian program remain highly classified, U.S. officials said. But others argued that the United States needed to share enough to convince China and India of the seriousness of the threat. During the Munich meetings the two men took in the information, officials said, and Mr. Wang repeated China’s usual lines about the importance of the peaceful use of outer space.
Mr. Blinken was attempting to replicate what American officials believe was a series of successful warnings to Mr. Putin in October 2022, when there was serious alarm in Washington that Russia was preparing to use a tactical nuclear weapon in Ukraine. Mr. Putin backed off the threats, though it is still unclear how much pressure he was under, especially from Mr. Xi, who has tightened his ties with Moscow.
Both the United States and Soviet Union briefly tested nuclear weapons in space before the ratification of the 1967 Outer Space Treaty, which bans the placement of nuclear weapons of any kind into orbit, as well as further nuclear detonations in space. A 1962 test by the United States, launched from Johnston Atoll in the Pacific Ocean, was particularly damaging. Exploding 250 miles into the atmosphere, the electromagnetic pulse destroyed electronics in Hawaii, disrupting telephone service there, and took out at least a half dozen orbiting satellites out of the sky, and damaged others.
Realizing how damaging the test was, a year later the United States and the Soviet Union signed the Limited Nuclear Test Ban Treaty, which prohibited nuclear testing in the atmosphere or outer space.
If Mr. Putin deployed the weapon into low-earth orbit, American officials fear it would do more than simply violate the 1967 treaty. It is one of the last remaining major arms control treaties still in effect. Biden administration officials have expressed concerns that if Russia violates it, other nations — such as North Korea — may follow suit.
For Mr. Putin, launching a nuclear weapon into space would escalate his growing confrontation with the United States and Europe. His inability to take over Ukraine, even with a far larger military, has vividly demonstrated the limits of Russia’s conventional forces. In the view of American and European intelligence agencies, that has made him more dependent on nuclear arms and cyberattacks, his most potent asymmetric weapons.
One senior intelligence official, who spoke on condition of anonymity to discuss sensitive nuclear matters, said that he thought Russia was developing space-based nuclear weapons because Mr. Putin believes none of his adversaries, including the United States, would risk a direct confrontation with Russia over the deployment of a nuclear-armed satellite.
Another intelligence official, speaking on condition of anonymity for the same reason, said that Mr. Putin might be betting that the threat of a nuclear explosion in space is different from the threat of the destruction of Los Angeles or London. The official added that Mr. Putin would be threatening hardware rather than people, which he may believe gives him more latitude to deploy the new satellite.
Publicly, the White House has only described the new Russian weapon as antisatellite technology, offering no details. But officials have insisted it poses no direct threat to human populations.
“We are not talking about a weapon that can be used to attack human beings or cause physical destruction here on earth,” John F. Kirby, a senior national security official, told reporters.
The new intelligence came to light after a cryptic public warning on Tuesday by Representative Michael Turner, Republican of Ohio and chairman of the House Intelligence Committee, that the U.S. had new intelligence about a “serious national security threat.”
Mr. Turner had been sending letters of concern about the antisatellite technology for weeks. He had grown frustrated and feared the administration was not taking it seriously enough, U.S. officials said, an allegation that administration officials deny.
Mr. Turner’s comments on Tuesday angered the White House and spy agencies because of their predictable effect: reporters scrambling to learn more about the intelligence began uncovering details of the antisatellite weapon.
On Thursday, Mr. Kirby said President Biden had ordered a diplomatic push, without describing the plan in detail.
“He has directed a series of initial actions, including additional briefings to congressional leaders, direct diplomatic engagement with Russia, with our allies and our partners as well, and with other countries around the world who have interests at stake,” Mr. Kirby said.
Eric Schmitt in Washington contributed reporting.
