Sweden is widely expected to apply for NATO membership after Russia's invasion of Ukraine sparked a surge in support, but many Swedes are uncomfortable with how quickly the decision-making process has gone.

The country is set to reverse a decades-old policy of non-alignment in the coming days, in lockstep with its neighbour and longtime security ally Finland which is due to officially announce its bid to join NATO on Sunday.

But for some, it feels rushed.

"I think everybody would have wanted more time for this because it's a huge issue," Stefan Lofven, Sweden's Social Democratic prime minister from 2014 to 2021, told AFP.

"At the same time, we know that you don't always get the time that you would like to have."

Part of the reluctance among some comes from the fact that neighbouring Finland has so quickly and overwhelmingly made up its mind in favour of joining the Western military alliance.

Finland, which shares a 1,300-kilometer (800-mile) border with Russia and is Sweden's closest defence cooperation partner, took a historic first step on Thursday when the president and prime minister came out in favour of joining NATO.

"I also wish that Finland could have waited. It's not an ideal situation, in the middle of a blazing war", former foreign minister Margot Wallstrom, a longtime opponent of membership who has grudgingly opened up to the idea, told AFP.

In a dig at Stockholm's stance, an image of Mr Bean as a Swedish official copying a Finnish official as he signs a NATO membership application has gone viral on social media.

Sweden, which was neutral in World War II, has stayed out of military alliances for more than 200 years, though it has forged closer ties with NATO since the 1990s.

Traditionally opposed to NATO membership, Prime Minister Magdalena Andersson's Social Democratic Party is expected to announce a historic reversal of its position this weekend, seen as paving the way for an application to join the alliance.

The swift turnaround has led to criticism that Stockholm is rushing through its national debate in order to align itself with Finland's calendar.

Sweden has forged closer ties with NATO since the 1990s
Sweden has forged closer ties with NATO since the 1990s POOL via AFP / EVELYN HOCKSTEIN

"It's not Sweden deciding the timeline, it's Finland, because they share a 1,300-km border with Russia", said Anders Lindberg, political editorialist at Aftonbladet, an independent social democratic daily.

Sweden is otherwise more accustomed to lengthy government-commissioned inquiries on major issues, aimed at fostering debate and building consensus so that decisions are broadly anchored in society.

In contrast, a security review on the pros and cons of NATO membership prepared by the parties in parliament was pulled together in just a few weeks.

The rapid U-turn is also remarkable given that the country "has built its identity on its neutrality" and military non-alignment, Lindberg added.

Support for NATO membership has soared in both Finland and Sweden since Russia's invasion of Ukraine.

But while a record 76 percent of Finns are in favour of joining NATO, Swedish public opinion is more divided, with recent polls indicating that between 50 and 60 percent back the idea.

Security experts say Sweden waited too long to debate NATO membership.

"The Social Democrats in Sweden have always said: 'We'll think about this when Finland joins'... because they thought Finland would never join", Elisabeth Braw, an expert on Nordic countries' defence at the American Enterprise Institute, told AFP.

At the same time, Finland's political leaders were a step ahead, leaving the door open for the "NATO option", or the possibility of joining quickly if needed.

"The responsibility for this situation rests with those people and those structures who have refused to discuss the matter of NATO until very recently", said Robert Dalsjo, an analyst at the Swedish Defence Research Institute (FOI).

"It's going to go fast. But it's going fast because this is a national security matter... We cannot delay forever because some people have not been interested in this matter before", he said.

For others, Finland has done Sweden -- which has historically and not without some arrogance considered itself a "big brother" to its smaller neighbour -- a huge favour by speeding up the decision.

"Without Finland, Sweden would never have joined NATO. Thank you, big brother!", daily Expressen wrote in an editorial Thursday.