Moscow said the move was “definitely” a threat and warned it was ready to respond. But Finland’s neighbour Sweden is also close to a decision on asking to join NATO after decades of following a neutral path.
Russia has partly tried to justify its invasion of Ukraine as a means to protect itself from NATO’s eastwards expansion.
However, Finnish President Sauli Niinisto said Russian President Vladimir Putin was responsible for Helsinki’s decision.
“You caused this. Look at the mirror,” he said prior to Thursday’s announcement.
Finland, which shares a 1,300 kilometre border and a difficult past with Russia, has gradually stepped up its cooperation with the North Atlantic Treaty Organization as a partner since Russia annexed Crimea in 2014.
But until the Feb. 24 invasion of Ukraine – which has seen thousands of people killed, cities razed, and forced millions to flee their homes – the Nordic country had refrained from joining NATO in order to maintain friendly relations with its eastern neighbour.
“Finland must apply for NATO membership without delay,” Niinisto and Prime Minister Sanna Marin said in a joint statement.
“We hope that the national steps still needed to make this decision will be taken rapidly within the next few days.”
The Finnish parliament will debate the announcement on Monday. A majority of lawmakers have already signalled their support for membership.
NATO Secretary General Jens Stoltenberg said any accession process would be “smooth and swift” and that Finland “would be warmly welcomed.”
After the announcement, Niinisto spoke with Ukrainian President Volodymyr Zelenskyy, who lauded Finland’s readiness to apply for NATO membership.
Russia, which had repeatedly warned both countries against joining the alliance, said on Thursday a Finnish entry into NATO was “definitely” a threat to it.
Kremlin spokesman Dmitry Peskov told reporters: “NATO expansion does not make our continent more stable and secure.”
Everyone wanted to avoid a direct a clash between NATO and Russia but Moscow was prepared to make a “decisive response” to any side that tried to hinder Russia’s operation in Ukraine, he said.
Asked what form Russia’s response would take, he replied: “Everything will depend on how this (NATO) expansion process of NATO expansion plays out, the extent to which military infrastructure moves closer to our borders.”
Poland and the Baltic countries, which were once ruled from Moscow and are now members of NATO, welcomed Finland’s announcement.
“Finland decided to join the Alliance. NATO is about to get stronger. Baltics about to get safer,” Lithuanian Foreign Minister Gabrielius Landsbergis said.
The head of the Estonian defence forces said Finland joining the alliance, and possibly Sweden, would boost NATO’s maritime and air defences.
“The most important addition to our defence plans is awareness of maritime and airspace. We will have a common picture, we will have our warning time reduced,” Brigadier General Enno Mots told Reuters on Thursday.
Denmark and Norway, fellow Nordic nations that are NATO members, welcomed Finland’s application and said they would push for fast NATO admission.
Ukraine’s fate has been particularly disturbing for Finland to watch as it fought two wars with Russia between 1939 and 1944, repelling an attempted invasion but losing around 10% of its territory in the subsequent peace agreement.
The view among Finns on NATO has changed rapidly since Russia initiated what it calls a “special operation” in Ukraine.
Public support for joining NATO has risen to record numbers over recent months, with the latest poll by public broadcaster YLE showing 76 per cent of Finns in favour and only 12 per cent against, while support for membership used to linger at only around 25 per cent for years prior to the war in Ukraine.
While military non-alignment has long satisfied many Finns as a way of staying out of conflicts, Russia’s invasion of sovereign Ukraine has led an increasing number of Finns to view friendly relations with Russia as an empty phrase.
Sweden’s ruling Social Democrats are expected to decide on Sunday whether to overturn decades of opposition to NATO membership, a move that would almost certainly lead to Sweden also asking to join the 30-nation alliance.
A poll by Demoskop in daily Aftonbladet on Tuesday showed support for NATO membership, which has been rising steadily among Swedes this year, at 61 per cent, up four percentage points from the end of April. In January, the figure was 42 per cent.