NATO members Denmark and Estonia said they would welcome Finland joining the alliance.
In a tweet posted by Denmark’s Ministry of State Thursday, Danish Prime Minister Mette Frederiksen said: "Strong messages from the President and Prime Minister of Finland. DK [Denmark] will of course warmly welcome Finland to NATO. Will strengthen NATO and our common security. DK will do everything for a rapid accession process after the formal application."
Earlier on Thursday, Finnish President Sauli Niinisto and Prime Minister Sanna Marin announced their support for NATO membership, saying in a joint statement: "Finland must apply for NATO membership without delay. We hope that the national steps still needed to make this decision will be taken rapidly within the next few days."
Meanwhile, Estonian Prime Minister Kaja Kallas said that Estonia supports "a rapid accession process" for Finland to join NATO, adding that Finland's potential application will have the country's "full support."
Kallas said in a tweet: "History being made by our northern neighbours."
"You can count on our full support. We support a rapid accession process. From our side will make necessary steps quickly," Kallas added.
Some background: Since the Russian invasion of Ukraine in February, public support for joining NATO in Finland has leaped from around 30% to nearly 80% in some polls.
Once parliament has approved the idea in principle and any other domestic legislative hurdles have been cleared, it is expected that NATO would invite Finland to negotiate its accession.
Finland shares an 800-mile border with Russia, which has warned against joining NATO by saying there would be consequences.