The Chief of the Air Staff has said the UK must "prepare today" for the possibility of future conflicts in space.
The warning came during the first day of the Defence Space 2020 Conference on Tuesday, where senior military leaders are exploring the possibilities and potential challenges of operating beyond Earth's boundaries.
Air Chief Marshal Sir Mike Wigston told delegates: "A future conflict may not start in space, but I am in no doubt it will transition very quickly to space, and it may even be won or lost in space, so we have to be ready and, if necessary, defend our critical national interests in space.
"If we don't think and prepare today, we won't be ready when the time comes."
Losing access to space-based services could affect the everyday lives of citizens, potentially blocking bank transactions and disrupting traffic signals.
General Sir Patrick Sanders, Commander of UK Strategic Command, said operating in space is vital for watching enemies too.
"ISRs [intelligence, surveillance, and reconnaissance] from space provides the ultimate high ground – it allows us not to see just over the hill but gets a satellite eye view of our targets and areas of interest," he said.
"[It gives] a live insight into the urban canyon – whilst maintaining a protected distance from the fight."
Last month, the US Space Force Chief said "it is clear" that space is now "a warfighting domain", warning Russia and China are two of the biggest threats.
NATO has categorised space as an operational domain.