David Cameron is hoping for further international backing for Britain to stay in the European Union as he sets off for what will be his final summit of world leaders before the June 23 referendum.
The UK's referendum is not on the official agenda for the two-day G7 in Japan, which kicks off on Thursday, but it is certain to feature heavily in conversations in the margins of the event and the Prime Minister will be hoping for a united show of support for a Remain vote from host Shinzo Abe and his fellow leaders.
On a visit to London earlier this month, the Japanese PM warned that Brexit would make the UK "less attractive" to investors from his country. And he said Japan would prefer to seal a free trade deal with the whole EU, rather than individual states.
Negotiations on the EU-Japan deal are high on the agenda for the summit in the Ise-Shima coastal resort, with G7 leaders expected to back early completion of talks which began in 2013. Both Mr Abe and European Commission President Jean-Claude Juncker have said they hope the deal - which Downing Street believes could be worth £5 billion a year to the UK - can be sealed by the end of 2016.
Mr Cameron is set to be at loggerheads with his host on broader economic policy, setting his face against Mr Abe's drive for a co-ordinated fiscal stimulus by G7 states to inject vigour into the lethargic global economy.
British officials said that Mr Cameron's priority will be to encourage the G7 to back "flexibility", with an approach permitting member states - the UK, US, France, Germany, Italy, Canada and Japan - to pursue economic policies appropriate to their particular circumstances.
The PM will push for action from the G7 on steel-dumping, to counter market distortions caused by over-production in China, which is threatening the viability of the industry in the UK and other countries around the world.
He will push for G7 condemnation of missile-testing in North Korea, and will seek support for the extension of sanctions against Russia when they come up for renewal in the summer. He will voice Britain's support for the extension into Libyan territorial waters of the EU's Operation Sophia mission against people-trafficking.
The final communique of the two-day summit is thought unlikely to give explicit G7 backing to the Remain side in the Brexit debate, but leaders including Mr Abe, US President Barack Obama and Canadian PM Justin Trudeau have already made clear their concerns about the negative consequences they expect from EU withdrawal.
A meeting of G7 finance ministers last week concluded that a potential UK exit would "complicate the global economic environment", while Germany's Wolfgang Schauble told reporters: "We were all of the opinion that it would be the wrong decision for the UK."
Mr Cameron was departing for Japan late on Tuesday to arrive in Ise-Shima on Wednesday evening, ahead of the welcome ceremony the following morning.