Finland and Sweden have taken another major step toward joining the NATO military alliance in response to Russia's unprovoked invasion of Ukraine, as Moscow warned it would watch the developments and respond accordingly.

Finland's parliament on May 17 overwhelmingly endorsed a bid to join NATO, abandoning more than seven decades of neutrality.

Lawmakers voted 188-8 in favor of the proposal put forward by Finnish President Sauli Niinisto and Prime Minister Sanna Marin, which came hours after neighboring Sweden signed a formal request to become a member of the Western alliance.

The vote was seen as a formality and lawmakers' approval wasn’t necessarily required, but Niniisto and Marin stressed that it was important for parliament to weigh in on such a "historic" move.

Earlier, Swedish Foreign Minister Ann Linde signed the official request to join NATO after Stockholm announced on May 16 it would seek membership in the 30-member alliance.

Finland is now expected to also sign a formal application and file it to NATO headquarters in the coming days together with Sweden.

The two countries have moved quickly toward joining NATO since Russia launched its unprovoked invasion of Ukraine on February 24.

The White House said on May 17 that U.S. President Joe Biden will host Niinisto and Swedish Prime Minister Magdalena Andersson for a meeting on May 19 to discuss the applications as well as the broader topic of European security.

The steps taken by the two Nordic neighbors have prompted warnings from Russia, which would see NATO expand right up to its western border.

Russian President Vladimir Putin said on May 16 that while Russia did not see Finland and Sweden's decision to join NATO as a threat, any deployment of military infrastructure there may trigger a response from Moscow.

Foreign Minister Sergei Lavrov on May 17 echoed Putin's comments, saying that Finland and Sweden joining NATO probably wouldn't make "much of a difference," as the two countries had long participated in the alliance's military drills.

But he warned that Russia would closely monitor NATO's activities in the future member states.

"NATO takes their territory into account when planning military advances to the east. So in this sense there is probably not much difference. Let's see how their territory is used in practice in the North Atlantic alliance."

While most NATO members are keen to welcome the two countries as quickly as possible, Turkey has potentially complicated their accession, with President Recep Tayyip Erdogan accusing them of failing to take a clear stance against terrorism, a reference to the harboring of Kurdish militants.

According to Justice Ministry sources quoted by the official Anadolu news agency, Sweden and Finland have failed to respond positively to 33 Turkish extradition requests over the past five years.

Sweden and Finland have said they plan to send delegations to Ankara to meet with Turkish officials, but Erdogan said they shouldn't bother.

"I am confident that with the help of constructive talks, the situation will be resolved," Niinisto told Sweden's parliament in an address to lawmakers on May 17, later adding during a question period, "I'm optimistic."

German Chancellor Olaf Scholz said on May 17 that he too was "confident" Turkey would support the move by both countries.

Bids to join NATO must be unanimously approved by all 30 members.