Britain has announced its biggest military spending increase since the Cold War, pledging to end the "era of retreat" as it seeks a post-Brexit role in a world Prime Minister Boris Johnson warns is more perilous than for decades.
Johnson said the extra spending reflected the need to upgrade military capabilities even as the COVID-19 pandemic pummels the economy and strains public finances.
He outlined plans on Thursday for a new space command, an artificial intelligence agency and said the navy would be restored as Europe's most powerful.
Outlining the first conclusions from a big review of foreign policy and defence, he announced an extra 16.5 billion pounds ($A29.9 billion) for the military over the next four years.
The defence budget is now just under 42 billion pounds a year.
"The era of cutting our defence budget must end, and it ends now," Johnson told parliament by video link from his Downing Street office, where he is isolating after contact with someone who tested positive for COVID-19.
"I have done this in the teeth of the pandemic, amid every other demand on our resources, because the defence of the realm and the safety of the British people must come first," he said.
"Our national security in 20 years' time will depend on decisions we take today ... the international situation is now more perilous and intensively competitive than at any time since the Cold War."