Finland's application to join NATO was the "natural step" to take following Russia's invasion of Ukraine, the Nordic country's foreign minister told a conference in Bahrain on Saturday.
Finland and Sweden dropped decades of military non-alignment and scrambled to become NATO members in May, after Russia's war.
All 30 NATO member states except Hungary and Turkey have ratified Finland's accession, which requires unanimous approval. Hungary has said it will support Finland's bid.
The decision to apply for NATO membership is "a result of the drastic change in our security environment", Finland's top diplomat Pekka Haavisto told the annual Manama Dialogue conference in Bahrain.
"Applying for NATO membership was... a natural step for us to take", he added.
In 2004, Finland said it would take the so-called "NATO option", in the event that its security environment "changes dramatically," the foreign minister said.
"And what would be more dramatic for a change than the attack of your neighbour towards a country of 50 million people?" Haavisto asked.
On Friday, Finland unveiled a plan to increase security on its border with Russia, including a 200-kilometre (124-mile) fence.
Some 200 kilometres of the 1,300-kilometre border would be fenced at a cost of around 380 million euros ($394 million), the border agency said.