Rishi Sunak is flying to the United States for meetings with President Joe Biden and Australian Prime Minister Anthony Albanese to flesh out a major defence deal.
The Prime Minister will arrive in San Diego on Sunday night to discuss Australia’s procurement of nuclear-powered submarines under the Aukus pact.
Mr Albanese is expected to announce a plan for a British-designed fleet, with US boats being purchased as a stop-gap measure.
While on the US west coast on Monday, Mr Sunak is also set to unveil the new integrated review of defence and foreign policy, which has been updated in the wake of Russia’s invasion of Ukraine.
Ahead of his trip, the Prime Minister said: “In turbulent times, the UK’s global alliances are our greatest source of strength and security.
“I am travelling to the United States today 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.
“As we launch the 2023 Integrated Review Refresh tomorrow, this is the future we want to deliver – a UK that is secure, prosperous and standing shoulder to shoulder with our partners.”
Last week Mr Sunak met French President Emmanuel Macron, smoothing out relations after they hit a low point with the September 2021 signing of the Aukus deal, which saw Australia ditch France in favour of an agreement with the UK and US.
Negotiations over the last 18 months have presented the Canberra government with a choice between a British or US design.
Reports suggest Australia could opt for a modified version of the British Astute-class submarine, plugging the gap until it enters into service in the 2040s with up to five American Virginia-class boats.
The UK hopes that Aukus will result in work for British shipyards such as BAE Systems’ facility in Barrow-in-Furness, Cumbria.
Mr Sunak’s first visit to the US as Prime Minister comes in another crucial week for his leadership, with Chancellor Jeremy Hunt setting out the Budget on Wednesday.
Defence minister James Heappey acknowledged there has been “robust” public and private clashes between the Ministry of Defence and Treasury over funding levels.
Defence Secretary Ben Wallace has been arguing for a multibillion-pound increase to his budget.
San Diego, in the state of California, where Mr Sunak used to live, is home to the US Pacific Fleet.
A Downing Street spokesman said: “He updated the Secretary-General on the UK’s Integrated Review Refresh, due to be published tomorrow, which will set out the Government’s evolving global strategy in light of Russia’s invasion of Ukraine and growing international volatility and competition.
“The Prime Minister also reaffirmed the UK’s intention to remain a leading contributor to Nato, recognising the importance of continuing to invest in collective Euro-Atlantic security.
“Secretary-General Stoltenberg welcomed the valuable role of the United Kingdom as a staunch Nato ally.
“The Prime Minister and Secretary-General agreed to continue working together in the lead-up to the Nato leaders’ summit in Vilnius this June, to ensure the alliance is addressing the threat on Europe’s eastern flank and is ready for the conflicts of the future.”