Boris Johnson is to fly to Finland and Sweden to discuss the Nordic countries’ ambitions to apply for membership of Nato.
The visit will be seen as a red rag to Moscow, after Russian president Vladimir Putin used fears of an expanded Nato alliance as a justification for his invasion of Ukraine.
Finnish president Sauli Niinisto is expected to confirm his country’s stance on membership on Thursday, while an announcement is expected from Sweden’s ruling Social Democrats on Sunday following consultations over the weekend.
Mr Johnson will meet his counterparts in Stockholm and Helsinki during a one-day trip on Wednesday, taking questions from the press in both countries.
After decades of neutrality, the question of Nato membership was thrust to the top of the political agenda in both Sweden and Finland by the invasion of Ukraine in February, which threw a harsh spotlight on the vulnerability of Russia’s neighbours to aggression from Moscow.
A formal application to join Nato could be made at the alliance’s June summit in Madrid and is likely to be fast-tracked, though getting the signatures of all 30 alliance members could take up to a year.
Setting out the UK’s position ahead of Mr Johnson’s visit, the prime minister’s official spokesperson said: “We support countries’ democratic capability to decide on things like Nato membership.
“We understand the positions of Sweden and Finland and that is why the prime minister is going to discuss these broader security issues.”