Finnish President Sauli Niinistö and Swedish Prime Minister Magdalena Andersson said that the two countries plan to submit their countries' Nato applications together at the alliance's headquarters in Brussels on Wednesday.
The leaders made the comments at a joint press briefing on Tuesday in Stockholm.
Niinistö said that Russia's invasion of Ukraine at the end of February prompted both Finland and Sweden to start working towards joining Nato.
"Previously, both [Finland and Sweden] and Russia thought that our non-alignment contributed to stability, but when Russia said that we weren't allowed to apply for Nato membership, that changed," Niinistö said.
"It meant that we had to do something, and after February 24 [the first day of Russia's ongoing invasion of Ukraine], it became clear what we needed to do," he continued.
Niinistö also noted Russia's recent decision to take a more relaxed stance than it previously had regarding Finland's and Sweden's potential accession to the alliance.
On Tuesday, Russian Foreign Minister Sergei Lavrov said Finland's and Sweden's accession into Nato would most likely make "not much difference," with President Vladimir Putin making a similar remark the previous day.
Niinistö suggested that change in tone may show that the leaders do not want to tell Russians that it has another problem on its hands.
The president said that he has considered whether there would be tough retaliation from Russia over Finland's Nato decision, adding that it does not appear to be the case but noted that the situation could still change.
Applying together
Andersson said that Sweden and Finland will submit their respective Nato applications at the military alliance's headquarters in Brussels on Wednesday.
"I am happy that we have taken the same path and we can do it together," she said. "Membership strengthens security for Sweden and the Baltic Sea region. The fact that we are doing this together means that we can contribute to security in northern Europe and take part in comprehensive Nordic cooperation,"
The leaders also addressed recent comments made by Turkish President Recep Tayyip Erdoğan that his country was not in favour of the Nordic countries joining Nato, citing concerns about the presence of "terrorists" in both countries.
Niinistö said both he and Andersson were trying to contact Erdoğan. He also noted that he was surprised by Turkey's changed attitude about the matter, saying that the country had previously expressed a positive attitude towards Finland's membership in Nato.
Andersson said that the two countries are prepared to travel to Turkey "to discuss and straighten out any question marks there may be."
Historic vote
Niinistö praised Finland's parliamentary parties' show of solidarity after the overwhelming majority of MPs voted to approve Finland's application to join Nato.
He noted that 94 percent out of 199 Members of Parliament voted for the motion.
Niinistö and his wife Jenni Haukio made an official state visit to Sweden on Tuesday.
Niinistö and Andersson are heading to the United States on Thursday to meet with US President Joe Biden to discuss their countries' pending Nato applications.
Niinistö said it will be very interesting to talk with Biden about the Nato application timetable.