Swedish Prime Minister Magdalena Andersson will seek broad support for an application to join Nato on Monday, she announced on Sunday after her party dropped its long-standing opposition to membership in the wake of Russia’s invasion of Ukraine.

Joining Nato was a distant prospect just months ago, but Russia’s attack on its neighbour has prompted both Sweden and Finland to rethink their security needs and seek safety in the military alliance they stood apart from during the Cold War.

The war in Ukraine shattered long-standing security policies and fuelled a wave of public support for Nato membership in both countries.

Following internal debates over the past week among the leadership of the Social Democrats, the biggest party in every election for the past century, Andersson said Nato entry was “the best thing for the security of Sweden and the Swedish people”.

“Non-alignment has served us well, but our conclusion is that it will not serve us as well in the future,” she said.

Supporters of joining the alliance will now command a broad majority in Sweden’s Riksdag with much of the Opposition already in favour, and a formal application by Andersson’s minority government will follow.

In Finland, President Sauli Niinisto confirmed the country’s intentions to apply on Sunday, saying the region would benefit. “We get security and we also extend it through the Baltic sea region and the entire alliance,” he told reporters in Helsinki.

At peace since the days of the Napoleonic wars, Sweden has been more reluctant to cast aside its non-alignment than Finland, which fought the Soviet Union in the 20th century.

Popular support for entry jumped to more than 60 per cent in Sweden from about 40 per cent before the war.

“I didn’t think it was necessary but now it feels better to have countries that would come to our defence,” said pastry shop worker Cecilia Wikstrom.

Tense wait

A membership application will herald a tense wait during the months it takes to be ratified by all Nato members — Turkey has already voiced its objections, though the alliance and the White House have said they were confident any security concerns could be addressed in the interim.

Britain’s foreign secretary Liz Truss on Sunday urged Nato allies to move fast to integrate new members.

Finland’s Niinisto expressed his readiness on Sunday to hold talks with his Turkish counterpart Tayyip Erdogan over his concerns. As a Nato member, Turkey can veto new members.

Both countries are already Nato partners, having taken part in allied exercises for years, and cast off strict neutrality on joining the European Union together in 1995. But they have until now reasoned peace was best kept by not publicly choosing sides.

Andersson cautioned on Sunday that the country would be “vulnerable” during the application process, before it is covered by the alliance’s collective defence clause. She did not specify what sort of threats were a cause for concern.

Russia has warned Sweden and Finland of “serious consequences” and that it could deploy nuclear weapons and hypersonic missiles in the European exclave of Kaliningrad if Sweden and Finland become Nato members.

The decision to slot in under the Nato umbrella would represent a setback for Moscow, with the war in Ukraine triggering the very kind of enlargement of the alliance on Russia’s borders that Moscow says it took up arms to prevent.