Finland s Interior Minister Krista Mikkonen presents the report on changes in the foreign and security policy environment of Finland after Russia s attack in Ukraine, in Helsinki, on April 13, 2022. AFP
The assault on Ukraine sparked a dramatic U-turn in public and political opinion in Finland and neighbouring Sweden regarding their long-held policies of military non-alignment.
Attempting to join NATO would almost certainly be seen as a provocation by Moscow, for whom the alliance's expansion on its borders has been a prime security grievance.
A government-commissioned report released Wednesday will examine the "fundamentally changed" security environment, according to Finland's foreign ministry, and will make its way through parliament.
An opening debate is planned for a week later.
It is expected to analyse different security options for Finland, which shares a 1,340-kilometre (830-mile) border with Russia.
Former prime minister and long-time NATO advocate Alexander Stubb believes Finland making a membership application is "a foregone conclusion".
Finland has a long history with Russia. In 1917 it declared independence after 150 years of Russian rule.
During World War II, its vastly outnumbered army fought off a Soviet invasion, before a peace deal saw it cede several border areas to the Soviet Union.
During the Cold War, Finland remained neutral in exchange for guarantees from Moscow that it would not invade.
Change of heart
So the turnaround in sentiment on NATO would have been unthinkable just a few months ago.
As recently as January, Prime Minister Sanna Marin said membership was "very unlikely" during her term.
But after two decades of public support for membership remaining steady at 20-30 percent, the war caused a surge in those in favour to over 60 percent, multiple polls showed.
Public statements gathered by newspaper Helsingin Sanomat suggest half of Finland's 200 MPs now support membership while only 12 oppose.
Others say they will announce a position after detailed discussions.
The government said it hopes to build a parliamentary consensus over the coming weeks, with MPs due to hear from a number of security experts.
Marin expects a decision "before midsummer", with many analysts predicting Finland could submit a bid in time for a NATO summit in June.
Any membership bid must be accepted by all 30 NATO states, a process that could take four months to a year.
Finland has so far received public assurances from secretary general Jens Stoltenberg that NATO's door remains open, and several members' support.
'Like changing religion'
Unlike Finland, Sweden shares no land border with Russia and the two countries have not been at war for two centuries.
Nonetheless, pro-NATO sentiment is also rising among Swedes who "are realising that they might find themselves in the same position as Ukraine, a lot of sympathy but no military help," said Robert Dalsjo, research director at the Swedish Defence Research Agency.
Many commentators expect Sweden and Finland will act in tandem on whether to join, but their leaders stressed they may reach differing decisions.
Sweden's ruling party this week announced a review of its long-held opposition to joining NATO.
"For the Social Democrats in Sweden to change opinion (on NATO) is like changing religion," former Finnish PM Alexander Stubb told AFP.
"And I'm not talking Protestant to Catholic, I'm talking Christian to Muslim."
Kremlin spokesman Dmitry Peskov warned Russia would take measures to "rebalance the situation" in the event of Finland joining.
Finland's President Sauli Niinisto said Russia's response could include airspace, territorial violations and hybrid attacks, which Finnish NATO proponents believe the country is well prepared to withstand.
"Russia will most certainly huff and puff," Dalsjo said, but added: "I don't think they will do anything violent.
"However, in the mood that (Russian President Vladimir) Putin is right now, I wouldn't rule it out entirely."