Rishi Sunak and the Japanese prime minister will sign what the UK Government said will be the most significant defence agreement between the two nations in more than a century.

The Prime Minister and his counterpart Fumio Kishida will sign a defence agreement at the Tower of London on Wednesday which will allow the UK and Japan to deploy forces in one another’s countries.

It will make the UK the first European country to have a reciprocal access agreement with Japan, with No 10 calling it the most important defence treaty between London and Tokyo since 1902.

The pact is part of the UK’s defence and foreign policy “tilt” towards the Indo-Pacific region following an integrated review in 2021 that recognised the growing impact of China in the area.

The access agreement has been years in the making, with former prime minister Boris Johnson agreeing a deal in principle in May during Mr Kishida’s first official visit to Britain.

Mr Sunak said the accord would “cement the UK’s commitment to the Indo-Pacific” and bolster economic security.

Officials said the defence agreement would allow both forces to plan and deliver larger and more complex military exercises and deployments.

Mr Sunak said: “In the past 12 months, we have written the next chapter of the relationship between the UK and Japan — accelerating, building and deepening our ties.

“We have so much in common: a shared outlook on the world, a shared understanding of the threats and challenges we face, and a shared ambition to use our place in the world for global good, ensuring our countries prosper for generations to come.

“This reciprocal access agreement is hugely significant for both our nations — it cements our commitment to the Indo-Pacific and underlines our joint efforts to bolster economic security, accelerate our defence co-operation and drive innovation that creates highly skilled jobs.

“In this increasingly competitive world, it is more important than ever that democratic societies continue to stand shoulder to shoulder as we navigate the unprecedented global challenges of our time.”

Mr Kishida’s visit to London is part of a whistle-stop tour to five G7 nations, marking Japan taking on the rotating presidency of the group for 2023.

His trip, which will see him visit France, Italy, the UK, Canada and finally the US in the space of five days, comes as Japan breaks from its post-war restraint to take on more offensive roles, with an eye toward China.

Japan announced last month it had adopted security and defence reforms, including a counter-strike capability that breaks from an exclusively self-defence-only principle that had been in place since its Second World War defeat.

While at the historic Tower of London, Mr Sunak and Mr Kishida will visit Japanese armour on display.

It was presented to King James VI in 1613 by the then-Shogun Tokugawa Hidetada of Japan.

The military gift was given to King James to mark the first ever trade agreement between England and Japan.

Putting pen to paper at the Tower will come weeks after the UK and Japan agreed, along with Italy, to develop the next generation of combat air fighter jets under the Global Combat Air Programme.

Last month, the UK and Japan also launched a new UK-Japan digital partnership to strengthen co-operation across cyber resilience, online safety and semiconductors.

As well as meeting to discuss defence and security challenges, the leaders are expected to discuss trade and the G7 response to Russia’s invasion of Ukraine, with the conflict approaching its first anniversary.