Finland's parliament voted overwhelmingly in support of joining Nato, one of the key steps on the path to membership.
Politicians approved legislation by 184 votes to seven, affirming that Finland accepted the terms of the Nato treaty.
Finland and Sweden both applied for Nato membership in the aftermath of the Russian war in Ukraine, but Wednesday's vote increases the likelihood Finland will enter the alliance before Sweden.
Another key step is unanimous ratification by all Nato members and on Wednesday, Hungary — the only country other than Turkey to not yet ratify both applications — began debating the Finnish and Swedish applications.
President Katalin Novak of Hungary said she supported the applications and urged MPs to make “a wise decision”.
But she added that it was a “complex decision, with serious consequences”, after Prime Minister Viktor Orban suggested MPs would first want talks on an EU-Hungary dispute.
The Finnish vote in the 200-seat Eduskunta legislature is the last required domestic hurdle to becoming part of the Nato military alliance.
Prime Minister Sanna Marin’s centre-left government initiated the vote, seeking to secure the approval of her country's politicians before an April 2 general election.
President Sauli Niinisto has pledged to sign Wednesday’s legislative decisions into law before the election.
Passing the bill does not mean that Finland will automatically join Nato first it does place a deadline for how long it can wait.
Finland and Sweden, which are close partners culturally, economically and politically, applied together to join Nato in May 2022.
Finland has remained militarily non-aligned since the Second World War, and Sweden has not been in a military conflict in the past 200 years.
Hungary has said it supports both applications but has not yet found time to ratify them. No date has been set for a vote.
A Hungarian junior foreign minister, Peter Sztaray, told MPs the enlargement would strengthen Nato and that they should vote on common sense instead of emotions.
Mr Orban has said some MPs were “not very enthusiastic” and accused Finland and Sweden of spreading “blatant lies” about the state of Hungary’s democracy.
“I’d ask that at the end it should be made clear that while we support Sweden and Finland’s accession to Nato in principle, we first need to have some serious discussion,” Mr Orban said last week.
Hungary has had EU funds withheld because of what Brussels regards as an erosion of democratic standards since Mr Orban came to power in 2010.
Turkey has expressed concerted opposition to the Nordic applications. It generally wants stronger action, mostly from Sweden, against groups that it considers terrorist organisations.
Swedish Prime Minister Ulf Kristersson said on Wednesday that Sweden needs a law that forbids participation in terrorist organisations — a move that could pave the way for Turkey’s approval.
“For far too long, Sweden has had too lax legislation regarding the possibility of participating in terrorist activities without it being a crime,” Mr Kristersson said.
Nato Secretary General Jens Stoltenberg said on Tuesday in Helsinki that adding Finland and Sweden as members was “a top priority” for the alliance. He urged Turkey and Hungary to ratify the Nordic countries’ accession.
Turkey has agreed to resume talks with Finland and Sweden in Brussels this month to iron out remaining issues.