Theresa May is to begin an official visit to Japan as she seeks to drum up trade and allay Brexit concerns.
Japan, which is negotiating a trade deal of its own with the EU, has been forthright in expressing concerns about Brexit’s impact on its UK-based firms, which employ about 140,000 people.
The UK cannot negotiate bilateral trade deals until it leaves the EU in 2019.
Japan is currently preoccupied with tackling the fallout from North Korea’s missile test over Hokkaido island.
The British prime minister has condemned North Korea’s actions as “reckless provocation”.
Speaking before starting her journey to Japan, she said: “These are illegal tests, we strongly condemn them and we will be working with Japan and other international partners to ensure that pressure is put on North Korea to stop this illegal action.”
Japan’s Prime Minister Shinzo Abe called it an “unprecedented” threat to his country, while US President Donald Trump said it was an act of “contempt”.
Mr Abe and Japan’s Emperor Akihito are expected to greet Mrs May when she arrives in Tokyo on Wednesday.
Mrs May’s trip to Japan is due to last for three days. She will be accompanied by a delegation of business leaders drawn from a range of sectors.
They will be keen to demonstrate their enthusiasm for new trade agreements with Japan. The UK will, however, be unable to sign any deal until it has left the EU
Mr Abe will be seeking assurances from Theresa May that Brexit will not be detrimental to Japanese businesses with bases in the UK.
Japan also wants to know what kind of relationship the UK will have with the EU post-Brexit.
That is the subject of ongoing negotiations in Brussels between Brexit Secretary David Davis and the EU’s chief negotiator Michel Barnier. Mr Barnier has urged the UK to start “negotiating seriously”.
In a report last year, the Japanese foreign minister warned Brexit could result in Japanese firms moving their European head offices out of Britain.
It urged the British government to deal with concerns in a “responsible manner”.
Nomura bank, Hitachi and carmakers Honda, Nissan and Toyota all have bases in the UK.
Earlier this year, Nissan said it would build two new models – the new Qashqai and X-Trail – at its Sunderland plant after the government promised that competitiveness would not be damaged by its EU exit.