Space has "fundamentally changed" in just a few years due to a growing arms race, a US general said, singling out China as the "most challenging threat", followed by Russia.

"We are seeing a whole mix of weapons being produced by our strategic competitors," General Bradley Chance Saltzman, the US Chief of Space Operations, told a select group of media, including AFP.

"The most challenging threat is China but also Russia," he said, speaking late Saturday on the sidelines of the Munich Security Conference, listing technologies including anti-satellite missiles, ground-based directed energy and orbit interception capacities.

"We have to account for the fact that space as a contested domain has fundamentally changed. The character of how we operate in space has to shift, and that's mostly because of the weapons (China) and Russia have tested and in some cases operationalised," he said.

His words carry even more weight given surging US-China tensions -- highlighted by tense exchanges in Munich Saturday between Secretary of State Antony Blinken and Beijing's top diplomat Wang Yi over a suspected Chinese spy balloon.

Blinken warned Wang that China must not repeat such an "irresponsible act" of sending a balloon over US airspace, while Wang said Washington's reaction -- it shot the craft down -- had damaged their countries' relations.

Space arms race

The space arms race is nothing new. As early as 1985, the Pentagon used a missile to destroy a satellite in a test.

Since then, the United States's rivals have been seeking to show they can compete -- China did the same in 2007, and India in 2019.

In February 2020, an American general noted that there were two Russian satellites placed into orbit that were tracking a US spy satellite.

And in late 2021, Russia destroyed one of its own satellites with a missile fired from Earth, in a show of force condemned as an irresponsible act by NATO chief Jens Stoltenberg.

"Adversaries are leveraging space... targeting and extending the range of their weapons," said General Saltzman.

"That's really the change that happens inside the domain."

Countries are increasingly secretive when it comes to their military activities in space but the race is such that in 2019, the year that the Pentagon launched its Space Force, it predicted that Russia and China could potentially overtake the United States.

Saltzman rejects the idea that Washington is behind.

But the fight has evolved, shifting from the idea of destroying satellites with missiles or "kamikaze" satellites, to that of finding ways of damaging them with laser weapons or powerful microwaves.

"I am always going to make sure that I preserve capabilities to do the most critical functions, like national command and control, or nuclear command and control," said the general.

'Responsible behaviour'

The Ukraine war has served as a reminder of the fundamental importance of space in conflicts today and in the future.

"Space is important to the modern fight," said General Saltzman.

"You can attack space without going (into) space, through cyber networks or other vectors. We have to make sure we are defending all these capabilities."

The growing military activity, combined with increasing commercial production, does however raise the potential problems of collateral damage, destructive debris and, more broadly, an international code of conduct.

Saltzman has never held talks with his Chinese and Russian counterparts, his aides told AFP. In Munich, he met Norway's defence minister and participated in a panel.

"We talked about responsible behaviour," he said. "There is proper way to behave in space, that is not debris-generating, that does not interfere, that has safe distances and safe trajectories, and we communicate when we have problems."

Space will become "more and more congested", he added.

"If we can operate with a clear understanding of what the standards are, we are going to be a lot safer."