Finland will apply for Nato membership, the country's president and government announced in a statement on Sunday.
The Nordic country, which shares a 1,340-kilometre border with Russia, has been inching towards a bid to join the alliance since Moscow ordered an invasion of Ukraine in February.
President Sauli Niinisto and Prime Minister Sanna Marin made the announcement at a joint news conference at the Presidential Palace in Helsinki, paving the way for an expansion of the 30-member military alliance.
The Finnish Parliament is expected to endorse the decision this week, but that is considered a formality.
A formal membership application will then be submitted to Nato headquarters in Brussels, Belgium.
“We have today made an important decision in good co-operation between the government and the president of the republic,” Ms Marin told reporters on Sunday.
“With the president of the republic, we have been in close contact with governments of Nato member states and Nato itself. I wish to thank the support we have received so far.”
Ms Marin said that while the decision had to be confirmed by Parliament, she trusted that MPs would debate the move “with determination and responsibility” when Parliament convenes on Monday. Finland's application “will be based on a strong mandate”, she said.
Projections show a large majority of the country's 200 MPs support the application.
Mr Niinisto hailed a “historic day” for Finland and said: “A new era is opening.”
During a phone call on Saturday, Russian President Vladimir Putin told Mr Niinisto that joining Nato would be a “mistake” because Finland faces “no security threats”.
Speaking to reporters in Helsinki on Sunday, Mr Niinisto said Mr Putin did not issue “any threats” to him during their phone conversation.
However, he noted that warnings had in recent weeks come from Russian sources and “even from Putin himself” about the Kremlin’s reaction to Finland becoming a member of Nato.
Mr Niinisto said when it comes to security matters “you have to be awake all the time and careful”.
Sweden is expected to make a decision in the coming days on whether it intends to apply to Nato.
Nato deputy secretary general Mircea Geoana on Sunday said “Finland and Sweden are already the closest partners” of the military alliance.
He was leading meetings in Berlin while Nato Secretary General Jens Stoltenberg recovered from the coronavirus.
