Finland's president and prime minister have called for the country to apply for Nato membership "without delay".
Sauli Niinisto and Sanna Marin said in a joint statement they expected a decision in the next few days.
The move comes amid a surge in public support for Nato membership following Russia's invasion of Ukraine.
Finland shares a 1,300-km (810-mile) border with Russia. Until now, it has stayed out of Nato to avoid antagonising its eastern neighbour.
Finland will formally announce its decision on Sunday after it has been considered by parliament and other senior political figures.
Sweden has said it will announce a similar decision on the same day.