The U.S. government has assessed that Russia recently launched a “counter space weapon” into orbit that could be used to attack satellites, U.S. officials said this week, adding to concerns about a new frontier for conflict between the nations.

Pentagon spokesman Maj. Gen. Patrick Ryder told reporters Tuesday that it had assessed that Moscow had launched a satellite into low Earth orbit last week that was “likely a counter space weapon presumably capable of attacking other satellites in low Earth orbit.”

“Russia deployed this new counter-space weapon into the same orbit as a U.S. government satellite,” Ryder said, noting that it could pose a possible threat to the satellite and would continue to be monitored. “We’ll continue to balance the need to protect our interests in space with our desire to preserve a stable and sustainable space environment.”

The Kremlin dismissed the claims Wednesday, suggesting that its recent space launch had not broken international law. “We are not violating anything,” Kremlin spokesman Dmitry Peskov told reporters Wednesday. “We have repeatedly advocated bans on the launch of any weapons into space; unfortunately, these initiatives have been rejected, including by the United States of America.”

The tension was sparked by a Russian launch carried out on May 17. Russia’s Ministry of Defense and state space agency Roscosmos posted statements last week confirming that Russia’s air and space forces had carried out a launch of what it described as a Soyuz-2.1b launch vehicle from Russia’s Plesetsk cosmodrome in the far north of the country.

Experts said the competing claims were inconclusive. Some said they would not describe the Russian launch as a weapon.

Jonathan McDowell, an astronomer at the Harvard & Smithsonian Center for Astrophysics, said the satellite “appears to be one of a series of Russian inspector satellites that ‘shadow’ U.S. spy sats at a generous distance of 50 km or more.”

“I do not believe that it is a weapon,” McDowell added. “I do not think it is a real threat to U.S. satellites.”

Russia launched a similar system several years ago in an apparent test, said Todd Harrison, a senior fellow with the American Enterprise Institute. “That system deployed a sub-satellite and then appeared to fire a projectile,” said Harrison. “It also appears that it can do close inspection and surveillance of satellites.”

Both sides were ambiguous in their descriptions of last week’s launch and its impact, said Bleddyn Bowen, an associate professor of international relations at the University of Leicester who has written books on space warfare and astropolitics.

“All we know is that [the satellite] it’s been put into a certain orbital flight path,” which presumably clashes with the United States’ interests, Bowen said. This could present a risk of “collision,” but “I wouldn’t rush to call it an antisatellite weapon yet,” he added.

However, the dispute shows the growing debate about warfare in space. Bowen said that with powers such as China, India, Russia and the United States active in space, “the risk of space warfare happening is very real.”

Russia and the United States have proposed rival resolutions to the U.N. Security Council in recent weeks, though neither passed. Russia vetoed a U.S.-led resolution last month that Washington said was designed to prevent a nuclear arms race in space.

The Security Council on Monday did not pass a Russia-backed proposal, co-sponsored by China, that aimed to prevent “for all time” the use of any weapons in space. Ahead of the vote, U.S. deputy ambassador Robert Wood accused Russia of “gaslighting” on the issue and stated Russia had launched likely “counter space weapons” into low orbit in 2019, 2022 and last week.

Russia’s Foreign Ministry called the results of the vote on the draft U.N. resolution “disappointing” on Tuesday and accused the United States of militarizing space.

“The United States and its allies, despite all the steps we have taken to consider their proposals … opposed our constructive, comprehensive initiative,” spokeswoman Maria Zakharova said. “They have once again demonstrated their true priorities in the space area, aimed not at keeping space free of weapons of any kind, but at placing weapons in outer space and turning it into an arena for military confrontation.”

A U.S. Space Command spokesperson said in a statement Wednesday that the Russian satellite was “likely a counter space weapon presumably capable of attacking other satellites in low Earth orbit.” The statement added that “even as Moscow backs space arms control negotiations, Russia continues to research, develop, test, and deploy a suite of counter space systems that threaten the safety and stability of the domain.”

Clay Moltz, a professor at the Naval Postgraduate School and author of books on space security and conflict, said space warfare “has already been occurring” for many years, largely in the form of jamming satellite signals. “But there have been no kinetic attacks or nuclear explosions except in national weapons testing programs,” he added.

“As space becomes more and more crowded … countries are nervous about possible attacks on their assets,” Moltz said. “Such a [space] war is certainly possible, but it would be damaging to all of humanity.”

Natalia Abbakumova contributed to this report.