British Prime Minister Rishi Sunak is flying to the United States on Sunday to meet US President Joe Biden and Australian Prime Minister Anthony Albanese in order to finalise details of a submarine pact aimed at countering China.
Britain will also publish an update to its security, defence and foreign policy, known as the Integrated Review, on Monday, setting out how it will respond to a world of increasing threats.
Since the last update in 2021, Russia has invaded Ukraine and tensions with China have risen.
Britain, the US and Australia announced the AUKUS (Australia-UK-US) plan in 2021 as part of efforts to counter China's growing military footprint in the Indo-Pacific region; the meeting in San Diego on Monday is expected to decide next steps for Australia to receive nuclear-powered submarines.
Sunak praised the AUKUS alliance on Saturday and said such partnerships exemplified Britain's approach.
"In turbulent times, the UK's global alliances are our greatest source of strength and security," he said.
"I am travelling to the United States to launch the next stage of the AUKUS nuclear submarine programme, a project which is binding ties to our closest allies and delivering security, new technology and economic advantage at home."
Under the initial AUKUS deal announced in 2021, the United States and Britain agreed to provide Australia with the technology and capability for nuclear-powered submarines.
Britain has said the deal, the first time the United States has shared its nuclear-propulsion technology since it did so with Britain in the 1950s, will help create new jobs in Britain and boost sluggish economic growth.